Barrier with integrated self-cooling solid state light sources

ABSTRACT

An integrated barrier or partition (e.g. suspended ceiling, wall, etc.) containing lightweight solid state light sources wherein the light emitting surface of the light sources are the primary heat dissipating surfaces of the light sources. The light sources comprising of light emitting diodes (LED) in thermal contact to light transmitting thermally conductive elements and combined with a reflector element to form a light recycling cavity, provide both convective and radiative cooling from their light emitting surfaces, eliminating the need for external appended heat sinks. Seismically safe suspended ceilings contain integrated lighting where the lighting adds less than one gram per square foot to the structure. The lighting, integrated into but without penetrating the barrier (suspended ceiling, ceiling, wall, floor, etc.), is nonflammable and does not promote flame spread or smoke generation. The lighting is easily incorporated into ceiling tiles, sheetrock, grid elements, painted and/or wallpapered surfaces.

REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority to U.S. Nonprovisional patentapplication Ser. No. 14/071,636, filed Nov. 4, 2013, and U.S.Nonprovisional patent application Ser. No. 14/071,630, filed Nov. 4,2013, the entireties of which are incorporated herein by reference.

BACKGROUND

Installing lighting in rooms, industrial spaces, suspended ceilings,walls, etc. has been problematic due the weight of the light sources andthe need to penetrate the barriers creating these enclosed illuminatedspaces. Solid state light sources have offered the promise of more lightweight lighting fixtures however that promise has not been fullyfulfilled. LEDs unlike conventional light sources such as incandescentbulbs cannot effectively cool themselves.

As such additional appended heatsinks or cooling means are required toprevent overheating. This increases the cost of not only the lightsources due to shipping costs and materials costs but also the fixturesthat use those light sources. It also results in heavy light sourcefixtures. In general, the need exists for articles and means which allowLEDs to be used without the need for additional heatsinking means. Theseappended heatsinks due to the size and unattractive appearance aretypically hidden in the barrier or other side of the barrier (ceiling,wall, etc.)

It is desirable to minimize the temperature difference between thejunction or active region of the semiconductor device and the ambientatmosphere to effectively cool small semiconductor devices. It is alsodesirable to minimize the surface area needed to dissipate the heatgenerated by the semiconductor devices to the ambient atmosphere. Whilehigh thermal conductivity materials can be used to spread the heat outover a very large area, these high thermal conductivity materials comewith the addition of significant weight and cost. In conventional LEDdevices several layers of interconnect exist between the LED die and thefinal light source. This approach is used because the lighting fixturemanufacturers have historically not been required or had the capabilityto wirebond, flip chip attach or even solder components into theirfixtures. Also the need to regularly replace light sources such asincandescent bulbs has led to a wide range of quick change interconnectslike sockets and pin based connector.

Lightweight self cooling solid state light sources would offersignificant benefits to fixture manufacturers. Incandescent bulbs forinstance are very lightweight generating over 1000 lumens while weighingonly 50 grams and as such can be easily held in place using even simplepins and sockets. For the typical LED sources, this is not the case. Theadded weight of the heatsink and the need for a low resistance thermalconnection between the LED package and the heatsink necessitates the useof complex multiple level interconnects. The need exists for LED lightsources which are lightweight and easily incorporated into a wide rangeof lighting fixtures without the need for additional heatsinking orcooling means.

Historically, light sources have cooled themselves as stated earlier. Inthe case of incandescent and fluorescent tubes, the glass envelopesurrounding the sources, and the filament or arc itself transfers theexcess heat generated via convection and radiation. An incandescent bulbglass envelope can exceed 1500 C and a halogen's quartz envelope mayexceed several hundred degrees Celsius. Radiative power scales as thefourth power of the temperature. A naturally convectively cooled surfacewith a surface temperature of 500 C in a 250 C ambient will transferonly about 5% of its energy to the surrounding ambient radiatively. Anaturally convectively cooled surface with a surface temperature of 1000C can transfer 20% of its energy to the surrounding ambient radiatively.The typical LED junction temperature for high powered devices can beover 1200 C and still maintain excellent life and efficiency. Forsurfaces with temperatures less than 1200 C the majority of the radiatedenergy is in the infrared with a wavelength greater than 8 microns.

Heat generated within the LEDs and phosphor material in typical priorart solid state light sources is transferred via conduction means to amuch larger heatsink usually made out of aluminum or copper. Thetemperature difference between the LED junction and heatsink can be 40to 500 C. The temperature difference between ambient and heatsinktemperature is typically very small given the previously statedconstraints on the junction temperatures of LEDs. This small temperaturedifference not only eliminates most of the radiative cooling but alsorequires that the heatsink be fairly large and heavy to provide enoughsurface area to effectively cool the LEDs. This added weight of theheatsink increases costs for shipping, installation and poses a safetyrisk for overhead applications. For example lighting in a typicalindustrial or office building will use troffers. These troffers whichare typically 2 foot by 4 foot house fluorescent tubes and weigh as muchas 30 pounds including the electronic ballasts. The four footfluorescent tubes by themselves weigh 200 grams each. These troffershave to be separately rigged and supported independent of the suspendedceiling. They pose a safety hazard in the event of a severe earthquake.They also typically pose a fire hazard as the diffusing elements whichinterface to the occupant side of the room are made out of flammablematerials (e.g. plastic). In newer installations light emitting diode(LED) based solid state troffers are being use to replace fluorescenttroffers. These solid state troffers however still require large andheavy appended heatsinks to dissipate the excess heat from the LEDs.They also use large plastic diffusers to spread the light out over alarger surface.

Surprisingly, much like conventional incandescent, halogen andfluorescent light sources, conventional solid-state light source are nottypically flame resistant or even conform to Class 1 or Class A buildingcode requirements. There are two types of fire hazards indirect (wherelamp/fixture is exposed to flames) and direct (where the lamp/fixturecreates the flames). Conventional solid-state lamps and fixtures canpose both indirect and direct fire threats because they use largequantities of organic materials that can burn.

Even though the LED die are made using inorganic material such asnitrides or AlinGaP which are not flammable, these LED die are typicallypackaged using organic materials or mounted in fixtures which containmostly organic materials. Organic LEDs or OLEDs not only are mostlyorganic but also contain toxic materials like heavy metals likeruthenium which can be released if burned. Smoke generated from theburning of these materials is not only toxic but one of the leadingcauses of death in fires due to smoke inhalation. Incandescent andfluorescent lighting fixtures typically are composed of sheet metalparts and use glass or flame retardant plastics designed specifically tomeet building code requirements. It is therefore advantageous that solidstate light sources be constructed of non-flammable and non-toxicmaterials especially in commercial applications like suspended ceilings.This is for the benefit of both for occupants and firefighters. Organicmaterials containing heavy metals and nanoparticles such as quantum dotsare especially problematic.

As an example, solid-state panel lights typically comprise acrylic orpolycarbonate waveguides which are edge lit using linear arrays of LEDs.A couple of pounds of acrylic can be in each fixture. Integrating thesefixtures into a ceiling can actually lead to increased fire hazard.Other troffer designs rely on large thin organic films to act asdiffusers and reflectors as seen in recent LED troffer designs. During afire these organic materials pose a significant risk to firefighters andoccupants due to smoke and increased flame spread rates. In many cases,the flame retardant additives typically used to make polymers more flameretardant that were developed for fluorescent and incandescentapplications negatively impacts the optical properties of waveguides andlight transmitting devices. Class 1 or Class A standards cannot be metby these organic materials. As such a separate standard for opticaltransmitting materials UL94 is used in commercial installations. The useof large amounts of these organic materials in conventional solid-statelight sources greatly increases the risks to firefighters and occupantsdue to their high smoke rate and tendency to flame spread when exposedto the conditions encountered in a burning structure. A typicalcommercial installation with a suspended ceiling contains 10% of thesurface area as lighting fixtures. The ceiling tiles are specificallydesigned to act as a fire barrier between the occupants and the plenumabove the suspended ceiling. The lighting fixtures compromise theeffectiveness of this fire barrier by providing a pathway for flames tobypass the ceiling tiles. For this reason even incandescent andfluorescent fixtures are typically required to have additional fireresistant covers on the plenum side of the ceiling. These fireenclosures increases costs and eliminates the ability to effectivelycool the light fixture from the plenum side of the ceiling. Given thatmost solid state troffers depend on backside cooling these fireenclosures lead to higher operating temperatures on the LED die andactually increase the direct fire hazard for solid state light sources.The large amount of organics in the solid state light fixtures candirectly contribute to the flame spread once exposed to flames eitherindirectly or directly. The need therefore exists for solid statelighting solutions which are Class 1 rated which can reduce the risks tooccupants and firefighters during fires and minimize the direct firehazard associated with something failing with the solid state lightbulbs.

The recent recalls of solid-state light bulbs further illustrate therisks based on the solid-state light sources themselves being a directfire hazard. In the recalls, the drive electronics over-heated, whichthen ignited the other organic materials in the light source. The needexists for solid state light sources which will not burn or ignite whenexposed to high heat and even direct flames. Existing incandescent andfluorescent lighting fixtures have over the last several decades foundthat the ideal solution is to construct the majority of the fixtureusing inorganic materials and to maximize the lumens per gram of thesource. A typical incandescent source emits greater than 30 lumens pergram and the source is self cooling based on both convective cooling andradiative cooling. A conventional solid-state light bulb emits less than5 lumens per gram and requires heatsinking means to transfer the heatgenerated by the LEDs and drive electronics to the surrounding ambient.The heatsink surfaces must be exposed to the ambient. In many cases suchas recessed can lights the heatsink surfaces are enclosed whichdramatically reduces the heat that can be transferred to the ambient.The high lumen per gram in the incandescent and fluorescent bulbs alsotranslates directly into less material to burn both indirectly anddirectly. Also, in solid-state light bulbs the drive electronics andlight source have the same cooling path and therefore heat generated inthe drive electronics is added to the heat generated by the LEDs. Theadded heat from the LEDs elevates the temperature of the driveelectronics and vice versa. In the recalls this has led to catastrophicresults igniting the organic materials used in the solid state lightsources. The coupling of the heat from the drive electronics and theLEDs combined with the large quantity of organic materials used createsa direct fire hazard when components like polymer capacitors and organiccoated wiring overheat and burn. Based on years of effort theincandescent and fluorescent sources have moved away from organic basedmaterials for exactly the reasons illustrated above. The solid statelighting industry needs to develop high lumen per gram solid state lightsources which not only improve efficiency but also do not represent afire hazard either indirectly or directly.

Commercial light applications are also subject to seismic, acoustic, andaesthetic requirements. Seismic standards require that suspendedceilings withstand earthquake conditions and more recently these samerequirements are being used to address terrorist attacks. In general,lighting fixtures must be separately suspended from the overhead deck insuspended ceiling applications because of their weight and size. Theneed exists for solid state lighting solutions which can be integratedand certified with suspended ceilings. Regarding acoustics the suspendedceiling dampens noise levels by forming a sound barrier in a mannersimilar to the fire barrier previously discussed. The lighting fixturesagain compromise the barrier created by the ceiling tiles because theycannot be directly integrated into the ceiling tiles or grid work. Theneed exists for solid state lighting sources which do not degrade theacoustic performance of the ceilings. Lastly, lighting is aesthetic aswell as functional. Market research indicates that troffers whilefunctional are not desirable from an aesthetic standpoint. The needtherefore exists for solid state lighting sources which provide a widerrange of aesthetically pleasing designs.

Suspended ceiling represent a large percentage of the commercial, officeand retail space. In this particular application 2 ft×2 ft and 2 ft×4 ftgrids are suspended from the ceiling and acoustic/decorative tiles aresuspended by the t shaped grid pieces. Lighting has typically been 2×2or 2×4 troffers which similarly are suspended on the t shaped gridpieces. The troffers are wired to the AC bus lines above the suspendedceiling. Each troffer comprises of a sheet metal housing, driver, lightsources, and reflective and diffusive elements. In the case of solidstate troffers additional heatsinking means or cooling means may also beincorporated into each troffer. To comply with building codes mostfixtures require additional fire containment housings which isolate thelighting fixture from the plenum space above the suspended ceiling. Ingeneral a standard troffer requires a minimum volume of 1 cubic foot fora 2×2 and 2 cubic feet for a 2×4. The typical lumen output is 2000lumens for a 2×2 troffer and 4000 lumens for a 2×4. In many instancesthe location of the light fixtures are put on a regular spacing eventhough uniform lighting throughout the area may not be required ordesirable. This is driven by the difficulty and costs associated withrelocating the troffers once installed. This leads to excess lightingwith its associated energy losses. The need exists for lightweightdiffuse and directional lighting fixtures for suspended ceilings thatcan be relocated easily and upgraded or changed as technology advances.

Recently Armstrong World Industries has introduced its 24 VDC DCFlexZone™ grid system. The T-shaped grid pieces provide 24 VDCconnections on both the top and bottom of the grid pieces. Theavailability of 24 VDC eliminates the need for a separate drivers andballasts for solid state lighting. The elimination or simplification ofthe driver allows for very lightweight and low volume light fixturesespecially for the cases where self cooling solid state light sourcesare employed. Lightweight and low volume, translate directly intoreduced raw material usage, fixture cost, warehousing costs, andshipping costs. By eliminating fixed metal housings and replacing themwith modular and interchangeable optical and lighting elements thatdirectly attach to an electrical grid system like Armstrong's DCFlexZone system costs can be reduced not only for the fixture itself butalso for the cost associated with changing the lighting. Close to 2billion square feet of commercial and retail suspended ceiling space isremodeled or created each year. The need exists for more flexibility inhow this space can be reconfigured.

Present fixtures require addition support to the deck of the buildingdue to weight and size constraints per seismic building codes. The needexists for field installable and user replaceable lighting fixtures thatcan be seismically certified with the grid so that the end user canadjust and reposition fixtures as the need arises. Under the presentrequirements, any changes to the lighting require that the ceilingpanels be removed and at a minimum additional support wires must beinstalled to the building deck before the fixture can be repositioned.This may also require a reinspection of the ceiling in addition to theadded cost for the change. The need exists for lightweight, robustlighting that can be easily adjusted by the end user without the needfor recertification and outside labor.

In evaluating the weight of light modules it is useful to utilize theconcept of lumens per gram. The lumens per gram of light fixtures canhave a major impact on manufacturing costs, shipping costs, and storagecosts due to reduce materials costs and handling costs. It could alsoallow for fixtures which can be directly attached to the grid of asuspended ceiling and still meet seismic standards without requiringadditional support structures which are commonly needed for existingtroffer type light sources

The need also exists for aesthetically pleasing high lumen per gramlight fixtures. For many applications, the lighting should be presentbut not draw attention to itself. This is not the case with trofferswhich immediately draw attention away from the other parts of theceiling. Therefore, there is a need for lightweight and compact lightingfixtures which address the above needs in suspended ceilingapplications. Again the thickness of the lighting module has a directimpact on the aesthetics of the installation. Existing linear solidstate sources require large light mixing chambers to spread the lightemitted by the LEDs. This dramatically increases the depth of theselight sources. In order for light panel modules to have a an emittingsurface close to the plane of the ceiling and not to protrude into theroom or office space below, the major portion of the light source modulemust be recessed into the suspension ceiling. The need exists for lowprofile, or thin lighting panels with thicknesses under 10 mm, which areattachable to the electrified grids. Ideally these lighting panels wouldbe field replaceable from the office space side of the installation byend users (and not require custom installers) and present anaesthetically pleasing and monolithic and uniform appearance.Essentially the ideal suspension ceiling lighting system would“disappear” into the ceiling from an aesthetic standpoint.

Finally the need exists for solid state lighting source which can meetor exceed Class 1 or Class A standards, meet seismic requirements, meetacoustic standards, be field adjustable, and be easily integrated in anaesthetically pleasing manner into commercial lighting applications.

Intelligent lighting allows for integration of lighting and sensors intothe lighting system. Lighting is required for all occupied areas andactive control of lighting via light harvesting and occupancy actuallycan lead to larger energy savings than the conversion from incandescentto solid state lighting. Presently lighting is a separate market andsupply chain from security, point of sale, and HVAC. As intelligentsystems permeate into retail, offices, manufacturing, and homes existinglighting suppliers may well be replaced by network suppliers. The needexists for lighting solutions which enable the integration of sensorsand networking in a wide range of installations.

As a large portion of the lighting market is based on upgrades, the needexists for retrofit systems that can be attached, mounted or otherwiseadhered to a wide range of barriers or barrier surfaces. Incandescentand halogen lighting require thermal isolation from combustiblesurfaces, fluorescent requires high voltage operation and is susceptibleto overheating and cold temperature issues. Existing solid statesolutions either have limited lumen output or require heatsinking orother cooling means such as fans to operate. Alternately panel basedsolid state lighting uses waveguide or led array approaches to createdistributed light sources. Waveguides are inherently flammable andrepresent a significant flame spreading issue along with high cost andweight. LED arrays transfer the heat generated into the mountingsurface, which can present a significant fire hazard. The need exist forretrofittable solid state light sources which overcome the deficiencieslisted above.

In general, integration of lighting into intelligent digital networks isbeginning to occur. There is a need for an intelligent solid stateelement which also emits light thereby bypassing the conventionallighting supply chain and enabling network companies the ability to usethe lighting grid, which must be in virtually every occupied area, asthe network grid. This solid state element needs to be aestheticallypleasing, lightweight, low cost, and compatible with both active andpassive electronics as well as emit light. Ideally this solid stateelement would be movable, retrofittable, and upgradable as well as emitlight. The network companies use technology which is almost entirelydirect current power. As such solid state lighting and network basedtechnology such as wireless, RFID, data, IR, and optical links havesimilar power needs. Unlike incandescent, fluorescent, and halogen lightsources the power requirements of solid state lighting can utilize lowvoltage power effectively.

Historically, lighting has been integrated into barriers or partitionsystems like suspended ceilings, walls, etc. as separate lightingfixtures. In suspended ceilings these are typically 2 foot by 4 foottroffers which are built to accommodate 4 foot long fluorescent tubes.The troffers emit 3000 to 4000 lumens and weigh several kilograms each.As such the troffers must be supported by separate support wires to thedeck above the suspended ceiling because the suspended ceiling cannotsupport the weight of the troffers using only the support grid itself.In addition, troffers because their supports are independently wired tothe deck and cannot be integrated into the suspended ceiling they aretypically set on a regular a spaced interval regardless of the lightingneeds of the room. As such many rooms are overlit leading to significantunnecessary energy usage. The troffers severely limit the aesthetic lookof the suspended ceiling. Existing troffers and conventional lightingalso require certified electricians for installation and maintenance.The need exists for barrier or partition systems which have integratedlighting where the light sources can be easily removed, retrofitted, andredistributed on the barrier to adjust for changes in light needs.

This invention discloses how these needs can be met with self coolingsolid state light sources which enable lower cost lighter weight barrieror partition systems for ceilings, walls, and floors.

SUMMARY

This invention discloses a barrier or partition to form suspendedceilings, ceilings, floors, and walls etc. containing integrated solidstate lighting. Most preferably low voltage grid systems based on selfcooling light sources are integrated into the partitions disclosed. Theself cooling light sources are based on LEDs and other semiconductorelements mounted onto or within light transmitting thermally conductiveelements such that the light emitting and cooling surfaces aresubstantially the same surfaces. The self cooling light source havecommon light emitting and cooling surfaces which eliminates the need foradditional heatsinking means. Appended heatsinks increases weight andcosts of not only the light fixture but the other structures needed tosupport the light fixture (e.g. supporting grid). The heat generated inthe self cooling light sources is dissipated through the light emittingsurface into the illuminated space of the installation. The light weightof the self cooling light sources enable lighter weight and lower costsuspension grids compared to conventional troffers and lightingfixtures. Because the light emitting surface and cooling surfaces aresubstantially the same the self cooling light sources can be mounted andintegrated into a wide range of barrier elements and or surfacesincluding those which may be considered combustible such as paintedsurfaces, wood, wallpapered surfaces and ceiling tiles. The self coolinglight sources are constructed of non-flammable materials beingsubstantially all inorganic such as alumina. The barriers may or may notcontain separate barriers elements like ceiling tiles, panels, floortiles or other construction materials. Barrier as used in thisdisclosure refers to panels, partitions, ceilings, floors, walls, etc.

This invention discloses a barrier with integrated lightingincorporating a non-flammable light recycling cavity light sourcecomprising, at least one reflector element and at least one lighttransmitting thermally conductive element wherein at least one lightemitting diode (LED) is within the light recycling cavity and in thermalcontact with and cooled by at least one light transmitting thermallyconductive element and optionally at least one wavelength conversionelement is also within the light recycling cavity formed by at least onereflector element and at least one light transmitting thermallyconductive element. These light recycling cavity solid state lightsources are cooled using substantially the same surfaces as the lightemitting surfaces. These light sources are particularly well suited forsuspended ceiling applications where the majority of the heat isdissipated into the occupant or office side of the suspended ceilinginstallation. Using this approach a substantially contiguous firebarrier can be maintained in the suspended ceiling especially for thecases where fire resistant ceiling tiles are used. This eliminates theneed for additional fire resistant shrouding.

The elimination of appended external heatsinks reduces weight and costof all the components within the suspended ceiling or barrier. The lightrecycling cavity light sources may be mounted onto the barrier supports(e.g. supporting grid for a ceiling) or and integrated directly into thebarrier element (e.g. ceiling tile). Using this approach self coolinglight sources outputting more than 30,000 lumens weigh less than 1Kilogram. This compares to a conventional solid state troffer which mayweigh more than 5 Kilograms and output only 4000 lumens. Waveguide basedtroffers or light panels weigh even more and also contain highlyflammable plastic materials which may increase flame spread and greatlyincrease smoke generation during fires. These conventional lightingsources must be separately suspended from the deck by support wires insuspended ceilings due to seismic and fire requirements. The lightweightself cooling nature of the light sources enables the direct integrationof the lighting into ceilings, suspended ceilings, walls, and floorswithout the need for additional support wires or cooling means. Apreferred embodiment is that the light sources connect to a distributedDC grid, however remote power sources may also be used to power thelight source. The light sources may also be configured for direct ACinput using anti-parallel or internal power converters.

The light recycling cavity light typically comprises of a lightrecycling envelope formed using at least one strongly scattering lighttransmitting thermally conductive element, at least one LED in thermalcontact with the at least one strongly scattering light transmittingthermally conductive element wherein at least one wavelength conversionelement and at least one interconnect for the at least one LED arewithin the recycling cavity envelope.

Alternately or simultaneously a substantially contiguous acousticalbarrier suspended ceiling may be formed comprising light recyclingcavity light sources which dissipate the majority of their heat into theoffice side of the installation. The active control of the acousticsincluding but not limited to noise blanking, background noise, andambience noise within the office side of the suspended ceiling may beintegrated into the recycling cavity light source in the form of anembedded speaker. In particular, low profile piezoelectric speakers canbe integrated into the light source. Alternately, alerts, music, andfire warnings can be integrated as well. Lightweight self cooling solidstate light sources with surface temperatures less than the buildingcode of 900 C are disclosed. These sources enable designers to move awayfrom standard 2 foot×2 foot or 2 foot×4 foot grid patterns dictated byfluorescent troffers and eliminates the need for additional supportwires. The lightweight self cooling light sources may be movable andremounted by the end user as required when used in conjunction with alow voltage power distribution system.

In another aspect, the invention may be a suspended ceiling systemcomprising: a support grid support comprising a plurality ofintersecting struts that form a plurality of grid openings, the supportgrid supported within an internal space of a building; a plurality ofceiling tiles mounted to the support grid and positioned in the gridopenings to collectively form a barrier, each of the ceiling tilescomprising a front surface facing an occupant portion of the internalspace of the building and a rear surface opposite the front surface; atleast one solid state light source comprising: at least one reflectorelement; at least one light emitting diode (LED); at least one lighttransmitting thermally conductive element, the light transmittingthermally conductive element providing a common light emitting andcooling surface to dissipate a majority of the heat from the solid statelight source, the common light emitting and cooling surface facing theoccupant portion of the internal space; and the solid state light sourceat least partially embedded in and supported by one of the ceilingtiles.

In yet another aspect, the invention may be an integrated ceiling paneland lighting apparatus comprising: a ceiling tile comprising: a frontsurface; a rear surface opposite the front surface; a side edgeextending between the front and rear surfaces of the ceiling tile; arecess formed into the front surface of the ceiling tile, the recessdefined by a recess sidewall and a recess floor surface, the recesssidewall extending from the front surface of the one of the ceilingtiles to the recess floor surface; at least one solid state light sourcecomprising: at least one reflector element; at least one light emittingdiode (LED); at least one light transmitting thermally conductiveelement, the light transmitting thermally conductive element providing acommon light emitting and cooling surface to dissipate a majority of theheat from the solid state light source, the common light emitting andcooling surface facing the occupant portion of the internal space; andthe solid state light source disposed within the recess and mounted tothe ceiling tile.

In a further aspect, the invention may be a suspended ceiling systemcomprising: a support grid comprising a plurality of intersecting strutsthat form a plurality of grid openings, the support grid supportedwithin an internal space of a building; a plurality of ceiling tilesmounted to the grid support and positioned in the grid openings tocollectively form a barrier, each of the ceiling tiles comprising afront surface facing an occupant portion of the internal space of thebuilding and a rear surface opposite the front surface, the frontsurfaces of the ceiling tiles defining a reference plane, the occupantportion of the internal space located below the reference plane; atleast one solid state light source comprising: at least one reflectorelement; at least one light emitting diode (LED); at least one lighttransmitting thermally conductive element, the light transmittingthermally conductive element providing a common light emitting andcooling surface to dissipate a majority of the heat from the solid statelight source, the common light emitting and cooling surface facing theoccupant portion of the internal space; and the solid state light sourcemounted to one of the struts so that at least a portion of the solidstate light source is located above the reference plane.

Disclosed are barriers with both lambertian and directional lightrecycling light sources wherein the light emission surface and coolingsurfaces are substantially the same.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B depict side views of prior art vertical and flip chipmounted LED packages and thermal schematics where the optical emissionis substantially in the opposite direction of the heat removal.

FIGS. 2A, 2B and 2C depict side views of self-cooling solid state lightsources using luminescent thermally conductive luminescent elements andinterconnects with thermal schematics of the present invention.

FIGS. 3A, 3B and 3C depict side views of a self-cooling solid statelight source with multiple die of the present invention.

FIGS. 4A, 4B and 4C depict side views of printed electricalinterconnects on luminescent thermally conductive elements for variousLED die types of the present invention.

FIGS. 5A, 5B, 5C and 5D depict side views of various shapes ofwavelength conversion elements of the present invention.

FIGS. 6A and 6B depict a side view of two different mountings for LEDson wavelength conversion elements of the present invention.

FIGS. 7A, 7B and 7C depict side views of printed interconnects on LEDdie of the present invention.

FIGS. 8A, 8B, 8C and 8D depict side views of various environmental sealsfor self cooling light sources of the present invention.

FIGS. 9A and 9B depict side views of die shaping for enhanced dual sidedextraction of the present invention.

FIGS. 10A and 10B depict a side view and a graph of blue and red die inwavelength conversion elements of the present invention.

FIG. 11 depicts a top view of a three pin self cooling light source ofthe present invention.

FIG. 12 depicts a top view of a self cooling light source with anintegrated driver of the present invention.

FIGS. 13A and 13B depict a side view and a perspective view of a selfcooling light source with additional cooling means of the presentinvention.

FIG. 14 depicts a top view of a self cooling light source with thermallyisolated sections of the present invention.

FIG. 15 depicts a top view of a self cooling light source with separatedrive scheme for blue and red die of the present invention.

FIGS. 16A and 16B depict graphs of subtractive red phosphor and additivered LED of the present invention.

FIG. 17 depicts a graph of the spectrum from a self cooling light sourcewith cyan and yellow LEDs of the present invention.

FIGS. 18A and 18B depict a side view and a perspective view of variousshapes with luminescent coatings of the present invention.

FIGS. 19A and 19B depict side views of optics for self cooling lightsource of the present invention.

FIGS. 20A, 20B, and 20C depict side views of means of modifying the farfield optical patterns of self cooling light sources of the presentinvention.

FIGS. 21A, 21B, and 21C depict side views of a light emitting patchsource and its use with waveguiding materials of the present invention.

FIG. 22 depicts a side view of a prior art light strip.

FIG. 23 depicts a side view of a prior art waveguide light panel.

FIG. 24 depicts a side view of a self cooling light strip where emittingsurface and cooling surface substantially the same.

FIG. 25 depicts a graph showing die temperature versus thermalconductivity of emitting/cooling surface.

FIG. 26 depicts a side view of a suspended ceiling installation.

FIG. 27 depicts a side view of a self cooling non-flammable light stripattached to suspended ceiling grid.

FIG. 28A depicts a side view of a self cooling non-flammable light panelintegrated into ceiling tile of a suspended ceiling.

FIG. 28B depicts a side view of an embedded self cooling light sourcewith the scrim of the ceiling tile taking the place of the reflector toform the light recycling cavity.

FIG. 28C depicts a side view of a holey light transmitting thermallyconductive element.

FIG. 29 depicts a side view of a suspended self cooling panel light.

FIG. 30 depicts a side view of a seismic installation of self coolinglight strip in suspended ceiling.

FIG. 31A is a schematic of a suspended ceiling system according to anembodiment of the present invention.

FIG. 31B is a perspective view of an integrated ceiling panel andlighting apparatus removed from the suspended ceiling system of FIG. 31A in an exploded state;

FIG. 31 C is a cross-sectional view of integrated ceiling panel andlighting apparatus of FIG. 31B according to an embodiment of the presentinvention.

FIG. 32A depicts a side view of a light recycling self cooling lightsource with a light transmitting thermally conductive translucentelement 3202 and a direct attach LED die 3204.

FIG. 32B depicts a side view of a light recycling cavity with a lighttransmitting thermally conductive element combined with a reflector3224.

FIG. 32C depicts a side view of a light recycling cavity with a lightredirecting reflector.

FIG. 32D depicts a side view of a light recycling self cooling lightsource with an additional waveguiding element that more or less fillsthe light recycling cavity.

FIG. 33 depicts a graph showing efficiency versus reflectivity inrecycling self cooling light sources.

FIG. 34 depicts a side view of decorative overlays on self cooling lightsources.

FIG. 35A depicts a side view of a light recycling self cooling lightsource with a reflector, a thermally conductive translucent element anda LED die.

FIG. 35B depicts a side view of a light recycling self cooling lightsource with a light transmitting thermally conductive luminescentelement.

FIG. 35C depicts a side view of a separate wavelength conversioncoating/element formed on a thermally conductive translucent element.

FIG. 35D depicts a side view of a self cooling light source without alight recycling cavity.

FIG. 36 depicts a side view of a push pin connector and self coolinglight source.

FIG. 37 depicts a side view of a scrim overlay for self cooling lightsource.

FIG. 38 depicts a side view of a modular rail based field replaceablelinear sources.

FIG. 39 depicts a side view of a magnetic connector for modular rail orgrid system.

FIG. 40 depicts a side view of a ceiling tile with recycling cavity.

FIG. 41 depicts a perspective view of a ceiling tile modular system withintegrated recycling cavity.

FIG. 42 depicts a side view of a suspended ceiling grid for fieldreplaceable self cooling light sources.

FIG. 43 depicts a side view of a snap fit linear source for grids,undercounter, aircraft, and ceiling lighting.

FIG. 44 depicts a side view of a self cooling lambertian solid statelight source with thermal insulation barrier.

FIG. 45A depicts a side view of a connector for self cooling lightsources with a reflector.

FIG. 45B depicts a side view of split reflectors with integral contacts.

FIG. 45C depicts a side view of a recycling cavity formed of side clips,a reflector 4564 and a translucent thermally conductive element.

FIG. 46A depicts a side view of a recycling light source with a lighttransmitting thermally conductive element and interconnects.

FIG. 46B depicts a side view of a flex circuit version of the selfcooling light source.

FIG. 47A depicts a side view of a plurality of light sources connectedtogether to form linear, shaped or large planar area light sources.

FIG. 47B depicts a side view of a plurality of light sources withconnectors comprising of at least one pin connector and at least onesocket connector.

FIG. 48 depicts a side view of a retrofit system for suspended ceilings.

FIG. 49A depicts a perspective view of a barrier utilizing a retrofitwall or floor installation of the light sources.

FIG. 49B depicts a side view of a power input means covered by coverlayer.

FIG. 50 depicts a perspective view of a removable modular wall systemwith integrated low voltage power grid.

FIG. 51 depicts a side view of a self supporting panel light.

FIG. 52 depicts a perspective view of an integrated low voltageretrofittable power grid.

FIG. 53A depicts a side view of a light recycling cavity with anintegrated reflective grid.

FIG. 53B depicts a side view of a light transmitting thermallyconductive element with associated elements.

FIG. 54A depicts a side view of a recycling light source with a holeylight transmitting thermally conductive element.

FIG. 54B depicts a side view of a recycling light source with a holeylight transmitting thermally conductive element and a reflector.

FIG. 54C depicts a side view of a recycling light source with a holeylight transmitting thermally conductive element and a reflector.

FIG. 55 depicts a side view of a shaped light transmitting thermallyconductive element which can be attached to a flat or non-flatreflective mounting surface.

FIG. 56 depicts a side view of a gimbaled self cooling light source.

FIG. 57 depicts a side view of a centrally support barrier system withbarrier elements.

FIG. 58 depicts a perspective view of a strip light made of multiplelight transmitting elements and single reflector.

FIG. 59A depicts a side view of a light recycling cavity source with thelight emitting surface also being the cooling surface.

FIG. 59B depicts a side view of another light recycling cavity sourcewith the light emitting surface also being the cooling surface.

FIG. 59C depicts a side view of a self-cooling light recycling sourcewith the LED package mounted within the recycling cavity but not on theinner surface of the light emitting portion of the holey recyclingcavity element.

FIG. 59D depicts a side view of a holey light recycling cavity elementwith LED package mounted onto a circuit board.

FIG. 59E depicts a side view of a light recycling cavity light sourcewith two or more translucent light transmitting thermally conductiveelements and reflectors.

FIG. 60 depicts a side view of a shaped self-cooling light source.

FIG. 61A depicts a side view of a self-cooling recycling light sourcewith thermal heat transfer elements within the recycling cavity.

FIG. 61B depicts a side view of a substantially contiguous thermaltransfer element surrounded by reflective interconnects.

DETAILED DESCRIPTION

This invention relates to a solid state light sources based on LEDsmounted on or within thermally conductive luminescent elements. Thethermally conductive luminescent elements provide a substantial portionof the cooling of the LEDs using both convective and radiative coolingfrom the light emitting surfaces of the thermally conductive luminescentelements. At least one thermally conductive luminescent element and atleast one reflector element form a recycling cavity which contains atleast one LED, at least one interconnect, a contact means, andoptionally at least one wavelength conversion means. The light source isstructured such that light emitted by the LED is emitted into therecycling cavity, bounces around within the recycling cavity and passesthrough and exits the light source through the at least one thermallyconductive luminescent element. The recycling within the light sourcecreates a very uniform emission from the surface of the at least onethermally conductive luminescent element. Wavelength conversion if usedmay occur within the recycling cavity, within or on a surface of the atleast one thermally conductive luminescent element, or external to thelight source. Recycling allows for the use of lower cost, lower in-linetransmission materials such as white body color alumina while stillmaintaining high efficiency. The recycling creates an efficient whitebody color volume emitter which luminesces uniformly while alsoproviding sufficient cooling to operate at high light output levels. Therecycling combined with a strongly scattering thermally conductiveluminescent element allows for the formation of thin lightweightdistributed light sources. Specifically, white body color thermallyconductive luminescent elements like alumina with in-line transmissionsless than 50% (1 mm thickness) are preferred to enhance intensityuniformity, enable large area light sources with thicknesses less than10 mm, and provide sufficient thermal spreading to enable naturalconvection and radiative cooling of sources emitting more than 100lumens per square inch off the light emitting surface alone. Even morepreferred is a strongly scattering thermally conductive luminescentelement with an in-line transmission less than 20% (1 mm thickness).Body color refers to the visual appearance of the light source when theLEDs are not emitting.

In general, this invention discloses an efficient, lightweight, thin,self cooling solid state light source based on strongly scattering lighttransmitting elements which are used to form a recycling cavity aroundat least one LED. The strongly scattering light transmitting elementsform a partially transmitting aperture, which increases the opticalpathlengths of the rays within the recycling cavity. Further thestrongly scattering light transmitting elements provide thermalspreading for the heat generated by the at least one LED, any wavelengthconversion losses, electrical resistance heating, or optical absorptionand transfers that heat to the surrounding ambient environment viaconvection, conduction, fluid transport, and/or radiative means. Thiscreates a self cooling light source in which substantially all the heatgenerated in the light source is dissipated using the light emittingsurface. By using the recycling cavity approach and low optical losselements, low cost materials like alumina can form light sources withgreater than 70% efficiency (LED optical watts to light source outputoptical watts) while simultaneously providing substantially all thecooling for the light source.

Electrical interconnect of the LEDs and other semiconductor devices arebased on opaque and/or transparent conductors to create low costself-cooling solid state light sources. The low cost self-cooling solidstate light sources can have printed thick film printed silverconductors with a reflectivity greater than 30%. The light emitted bythe LEDs and/or LED packages is redirected by optical elements includingbut not limited to reflectors, reflective diffuse elements, and otherthermally conductive luminescent elements. For clarity it should benoted that luminescence is defined as allowing the emission of light.This can be based on simple transmission of the light emitted from theLEDs or LED packages, wavelength conversion of the light emitted fromthe LEDs or LED packages or some combination of both transmission orwavelength conversion. However, it is noted that virtually all materialsexhibit some level of wavelength conversion to UV and blue wavelengths.As an example, standard alumina (Al2O3) typically has chromium dopingwhich when exposed to 450 nm blue light emits narrowband red light. Thisin fact formed the basis of the first laser, which was chromium dopedsapphire (ruby). A key attribute of this invention is the formation ofefficient recycling cavities as disclosed in Zimmerman U.S. Pat. No.7,040,774 included by reference.

In recycling optical cavities multiple bounces or reflections arepurposefully caused to occur. If the cavity is formed using materialswith low enough optical absorption losses, the efficiency can be veryhigh even though the material may be strongly scattering. This inventiondiscloses the formation of recycling optical cavities in which at leasta portion of the recycling cavity is constructed of translucentthermally conductive elements. This is based on the recognition thateven materials typically considered opaque can be used to form efficientemitters if optical absorption is minimized. The importance of thisdiscovery is that low cost materials such as white body color aluminacan now function as translucent thermally conductive emitters with orwithout wavelength conversion. The ability to form white body color oreven off-white body color light sources is important from both anaesthetic and marketing standpoint. Consumers prefer white body color oroff-white body color light sources for mainly applications due to theirfamiliarity with incandescent and fluorescent lamps. As such thermallyconductive luminescent elements with white or off-white body colors whenthey are not emitting light from the LEDs and/or LED packages arepreferred. This can be further extended to include a wide range of bodycolors and patterns when non-homogenous thermally conductive luminescentelements are used such as reflectors with arrays of holes. The use oftexture and other outer surface treatments to create various aestheticlooks is also disclosed. In particular, the creation of thermallyconductive luminescent elements which match or are aesthetically similarto ceiling tiles is disclosed. In general, the ability to create a widerange of body colors for the thermally conductive luminescent element isa preferred embodiment of this invention.

In this configuration the light emitting surfaces also function as thecooling surfaces. As an example, alumina, TPA, or single crystalsapphire are all Al2O3 with simply different crystal structures. Aluminabecause of scatter elements (porosity and crystal size) is notconsidered an optical material due to its low in-line transmission andis generally considered opaque. However because of it usage in substratematerials it is available in high volume for less than 10 cents persquare inch in thickness ranging from hundreds of microns to a couplemm. At these thicknesses in-line transmission is typically less than 20%(1 mm thickness). TPA is a polycrystalline version that requiressignificantly different firing conditions and material purity and a hostof filings exist on how to make this material economically especiallyfor halogen and metal halide lamps. In similar thicknesses to aluminaTPA has in-line transmission greater than 80%. Sapphire is still anotherform of Al2O3 based on single crystal growth which is even moreexpensive than TPA and orders of magnitude more expensive than alumina.In line transmission for sapphire is similarly greater than 80% againfor similar thickness. Using the recycling cavity approach disclosed inthis invention overall light source efficiency using alumina is greaterthan 70% with TPA and sapphire being only 5% higher at 75% even thoughthere is a 4× difference in in-line transmission efficiency. This is dueto the understanding that scatter does not necessarily lead to anabsorption loss if recycling is allowed to occur. It should be notedthat the intensity uniformity is very poor for the TPA and sapphirespecifically because there is very little recycling occurring comparedto the strongly scattering alumina when identical source geometries areused.

Also disclosed is a self cooling light source of the invention, whichcomprises at least one light-emitting diode (LED) die and at least onethermally conductive luminescent element. In this case the at least onethermally conductive luminescent element forms an envelope around the atleast one light emitting LED. The luminescent element includes anelectrical interconnect and can perform multiple functions: as awavelength converter, converting at least a portion of the light emittedby said LED die to a different wavelength range, as an optical waveguidefor light emitted by said LED die, and as a heat spreading element,spreading heat generated by said LED die over a greater cross-sectionalarea. Finally the luminescent element provides a high emissivity layer,for optimal coupling of emitted light from the light source.

The thermally conductive luminescent element can be used to completelyor partially eliminate the need for any additional heatsinking means byefficiently transferring and spreading out the heat generated in LED andluminescent element itself over an area sufficiently large enough suchthat convective and radiative means can be used to cool the device. Inother words, the surface emitting light also convectively andradiatively cools the device. The thermally conductive luminescentelement can also provide for the efficient wavelength conversion of atleast a portion of the radiation emitted by the LEDs.

The present invention may also be defined as a self cooling solid statelight source comprising at least one light-emitting diode (LED) die andat least one thermally conductive luminescent element bonded to the atleast one LED die; wherein heat is transmitted from the light source inbasically the same direction as emitted light. More specifically, lightis emitted from the LED die principally in a direction through the atleast one luminescent element, and heat generated in the light source istransmitted principally in the same direction as the direction of lightemission. Heat is dissipated from the light source by a combination ofradiation, conduction and convection from the at least one luminescentelement, without the need for a device heatsink.

Optionally, the luminescent thermally conductive element can providelight spreading of at least a portion of the radiation from the LEDsand/or radiation converted by the thermally conductive luminescentelements via waveguiding. A thermally conductive luminescent elementacts as a waveguide with alpha less than 10 cm-1 for wavelengths longerthan 550 nm. In this case, the LEDs with emission wavelengths longerthan 550 nm can be mounted and cooled by the thermally conductiveluminescent elements and also have at least a portion of their emissionefficiently spread out via waveguiding within the thermally conductiveluminescent element as well.

Thermally conductive luminescent elements with wavelength conversionelements used with InGaN and AlInGaP LEDs can convert at least a portionof the InGaN spectrum into wavelengths between 480 and 700 nm. Singlecrystal, polycrystalline, ceramic, and/or flamesprayed Ce:YAG, StrontiumThiogallate, or other luminescent materials emitting light between 480and 700 nm and exhibiting an alpha below 10 cm-1 for wavelengths between500 nm and 700 nm can be a thermally conductive solid luminescent lightspreading element.

The mounting of InGaN and AlInGaP LEDs can form solid state extendedarea light sources with correlated color temperatures less than 4500 Kand efficiencies greater than 50 L/W and optionally color renderingindices greater than 80 based on these thermally conductive lightspreading luminescent elements.

One embodiment of this invention is a luminescent thermally conductivetranslucent element having a thermal conductivity greater than 1 W/mKcomprising of one or more of the following materials, alumina, ALN,Spinel, zirconium oxide, BN, YAG, TAG, composites, porous metalreflectors and YAGG. Optionally, electrical interconnects maybe formedon at least one surface of the luminescent thermally conductivetranslucent element to provide electrical connection to the LED.

The luminescent thermally conductive element can have a thermalconductivity greater than 1 W/mK and have an emissivity greater than0.2. A self cooling solid state light source can have at least oneluminescent thermally conductive element with a thermal conductivitygreater than 1 W/mK and an emissivity greater than 0.2. A self coolingsolid state light source can have an average surface temperature greaterthan 500 C and a luminous efficiency greater than 50 L/W. Optionally, aself-cooling solid state light source can have an average surfacetemperature greater than 500 C and a luminous efficiency greater than 50L/W containing at least one luminescent thermally conductive elementwith a thermal conductivity greater than 1 W/mK and an emissivitygreater than 0.2. A self-cooling solid state light source can dissipategreater than 0.3 W/cm2 via natural convection cooling and radiationcooling.

Luminescent thermally conductive elements can be formed via thefollowing methods: casting, metal forming, laser cutting, stamping,crystal growth, sintering, coating, fusible coating, injection molding,flame spraying, sputtering, CVD, plasma spraying, melt bonding, andpressing. Pressing and sintering of oxides with substantially one phasewill improve translucency based on a luminescent powder. Alternately, atranslucent element with a thermal conductivity greater the 1 W/mK andan alpha less than 10 cm-1 can be coated with a luminescent layer formedduring the sintering process or after the sintering process. Singlecrystal or polycrystalline materials, both luminescent andnon-luminescent, can be the thermally conductive luminescent element.Specifically TPA (transparent polycrystalline alumina), Spinel, cubiczirconia, quartz, and other low absorption thermally conductivematerials with a luminescent layer can be formed during or afterfabrication of these materials. Techniques such as pressing, extruding,and spatial flame spraying can form near net shape or finished parts.Additional luminescent layers can be added to any of these materials viadip coating, flame spraying, fusing, evaporation, sputtering, CVD, laserablation, or melt bonding. Controlled particle size and phase canimprove translucency. In the case of metal films with holes the size ofthe hole and spacing can be uniform or non-uniform. Non-homogenousthermally conductive luminescent elements may comprise metal foils withhighly reflective inner surfaces with holes. A non-homogenous array ofholes, where the open hole area represents 20% of the surface area isroughly equivalent to a piece of alumina with an in-line transmission of20%. The higher thermal conductivity of the metal foils allow for muchthinner thickness while still retaining reasonable lateral thermalconductivity.

Coatings can improve the environmental and/or emissivity characteristicsof the self-cooling light source, particularly if the coating is a highemissivity coating with and without luminescent properties. Singlecrystal, polycrystalline, ceramic, coating layers, or flame sprayed canbe used both as a coating and as the bulk material Ce:YAG, with a highemissivity or environmental protective coating. In particular,polysiloxanes, polysilazanes and other transparent environmentalovercoats can be applied via dip coating, evaporative, spray, or othercoating methods, applied either before or after the attachment of theLEDs. Additional luminescent materials can be added to these overcoatssuch as but not limited to quantum dots, luminescent dyes (such as Eljenwavelength shifter dyes), and other luminescent materials. A wide rangeof the coatings for aesthetic and improved radiation are possible withnon-homogenous thermally conductive luminescent elements, because theinner and outer surfaces of the element are isolated from each other. Itis preferred that the non-homogenous thermally conductive luminescentelements have a high reflectivity surface for the surface, which formsthe inner walls of the recycling cavity. The outer surface of thenon-homogenous thermally conductive luminescent elements can be anycolor up to and including black.

Wireless power transfer elements, power conditioning element, driveelectronics, power factor conditioning electronics, infrared/wirelessemitters, and sensors can be integrated into the self-cooling solidstate light source.

A self-cooling solid-state light source can have a luminous efficiencygreater than 50 L/W at a color temperature less than 4500K and a colorrendering index greater than 70. The self-cooling solid-state lightsource can have a surface temperature greater than 400 C, convectivelyand radiatively cooling more than 0.3 W/cm2 of light source surfacearea, and having a luminous efficiency greater than 50 L/W.

A self-cooling solid-state light source can have a luminous efficiencygreater than 50 L/W at a color temperature less than 4500K and a colorrendering greater than 85 containing both blue and red LEDs. At leastone luminescent thermally conductive element with an alpha less than 10cm-1 for wavelengths longer than 500 nm is used in the self coolingsolid state light source containing at least one blue and at least oneLED with emission wavelengths longer than 500 nm. Additional luminescentmaterials in the form of coatings and/or elements including, but notlimited, to phosphor powders, fluorescent dies, wavelength shifters,quantum dots, and other wavelength converting materials, can furtherimprove efficiency and color rendering index.

Aspect ratios and shapes for the solid state light source can be,including but not limited to, plates, rods, cylindrical rods, spherical,hemispherical, oval, and other non-flat shapes. Die placement canmitigate edge effects and form more uniform emitters. Additionalscattering, redirecting, recycling, and imaging elements can be attachedto and/or in proximity to the solid state light source designed tomodify the far field distribution. Additional elements can be attachedto the solid state light source with a thermally conductivity greaterthan 0.1 W/mK such that additional cooling is provided to the solidstate light source via conduction of the heat generated within the solidstate light source to the additional element and then to the surroundingambient. An external frame can provide mechanical support, can beattached to the solid state light source, and/or can provide an externalelectrical interconnect. Multiple solid state sources arranged with andwithout additional optical elements can generate a specific far fielddistribution. In particular, multiple solid state sources can bearranged non-parallel to each other such that surface and edgevariations are mitigated in the far field. A separation distance betweensolid state light sources faces of greater than 2 mm is preferred tofacilitate convective cooling. Mounting and additional optical elementscan enhance convective cooling via induced draft effects.

In this invention, thermally conductive luminescent elements on to whichsemiconductor devices are mounted are used to effectively spread theheat out over a sufficient area with a low enough thermal resistance toeffectively transfer the heat generated by the semiconductor devices andthe thermally conductive luminescent element itself to the surroundingambient by both convection and radiative means. In this invention, thesurface emitting light convectively and radiatively cools the device.

The thermally conductive luminescent element can also provide for theefficient wavelength conversion of at least a portion of the radiationemitted by the LEDs. Optionally, the luminescent thermally conductiveelement can provide light spreading of at least a portion of theradiation from the LEDs and/or radiation converted by the thermallyconductive luminescent elements. The thermally conductive luminescentelements act as waveguides with alpha less than 10 cm-1 for wavelengthslonger than 550 nm. In this case the LEDs with emission wavelengthslonger than 550 nm can be mounted and cooled by the thermally conductiveluminescent elements and also have at least a portion of their emissionefficiently spread out via waveguiding within the thermally conductiveluminescent element as well.

Disclosed is a self cooling solid state light source containing anoptically transmitting thermally conductive element with a surfacetemperature greater than 500 C and a surface area greater than thesemiconductor devices mounted on the optically transmitting thermallyconductive element. Even more preferably a self cooling solid statelight source containing at least one optically transmitting thermallyconductive element with a surface temperature greater than 1000 C and asurface area greater than the surface area of the mounted semiconductordevices. The optically transmitting thermally conductive element may becoupled with a reflector to form a recycling cavity. In this case atleast one LED is mounted to the optically transmitting thermallyconductive element such the heat generated by the LED is distributedlaterally by the optically transmitting thermally conductive element andthereby transmitted off the surface of the optically transmittingthermally conductive element to the surrounding ambient. Optionally, awavelength conversion element is also used within the recycling cavityformed by the optically transmitting thermally conductive element andreflector to convert at least a portion of the emission generated by theLED also within the recycling cavity to a different wavelength range.The emission from the LEDs and any optional wavelength conversionelement exits the recycling cavity through the optically transmittingthermally conductive element and the heat generated within the lightsource is dissipated to the office side of the installation off thesurface of the optically transmitting thermally conductive element. Theformation of reflective interconnects for providing power to the LEDs onthe optically transmitting thermally conductive element is alsodisclosed. Silver is a preferred material for the reflectiveinterconnect. It should be noted that by using a recycling cavityapproach and high reflectivity materials within the recycling cavity,what would typically be considered opaque materials like alumina can beused in thicknesses up to 1 mm for the optically transmitting thermallyconductive element because multiple reflections are possible withoutsignificant losses. As an example, 500 micron 96% alumina substrateshave an in-line transmission of less than 20% but when used as anaperture to a recycling cavity light source has an efficiency of over70%. Even though only 20% is transmitted each time rays impinge on thealumina within the recycling cavity if the absorption losses areminimized by having a highly reflective reflector (such as Alanod™),reflective interconnect traces, reflective LEDs, low loss wavelengthconversion elements, and low loss alumina 10 s if not 100 s bounces canoccur within the recycling cavity. This approach not only creates highefficiency solid state light sources, it also improves the brightnessuniformity of the source, allows for indirect positioning of the LEDs,lower color temperature for a given amount of wavelength conversionmaterial, and the ability to generate a wide range of external bodycolors.

Also preferred is a self cooling solid state light source containing atleast one optically transmitting thermally conductive luminescentelement with an average thermal conductivity greater than 1 W/mK. As anexample, YAG doped with 2% Cerium at 4 wt % is dispersed into an aluminamatrix using spray drying. The powders are pressed into a compact andthen vacuum sintered at 15000 C for 8 hours, followed by hot isostaticpressing at 16000 C for 4 hours under argon. The material is diamond sawdiced into 1 mm thick pieces which are ½ inch×1 inch in area. The partsare laser machined to form interconnect trenches into which silver pasteis screen printed and fired. The fired silver traces are then lapped toform smooth surface to which direct die attach LED die are soldered.Pockets are cut using the laser such that two pieces can be sandwichedtogether thereby embedding the direct die attach LED die inside twopieces of the ceramic Ce:YAG/alumina material. In this manner, a selfcooling light source is formed. The direct die attached LED(s) areelectrically interconnected via the silver traces and thermallyconnected to the ceramic Ce:YAG/alumina material. The heat generatedwithin the LEDs and the ceramic Ce:YAG/alumina material is spread outover an area greater than the area of the LEDs. In this example, powerdensities greater than 1 W/cm2 can be dissipated while maintaining ajunction temperature less than 1200 C and surface temperature on theceramic Ce:YAG/alumina material of 80 to 900 C based on naturalconvection and radiative cooling. As such a ¼ inch×½ inch solid statelight source can emit over 100 lumens without any additional heatsinkingor cooling means.

Materials with emissivities greater than 0.3 are preferred to enhancethe amount of heat radiated of the surface of the solid state lightsource. Even more preferable is an emissivity greater than 0.7 forsurface temperatures less than 2000 C. A naturally convectively cooledsurface with a natural convection coefficient of 20 W/m2/k with asurface temperature of 500 C in a 250 C ambient will transfer about 25%of its energy to the surrounding ambient radiatively if the surfaceemissivity is greater than 0.8 and can dissipate approximately 0.08W/cm2 of light source surface area. A similar naturally convectivelycooled surface with a surface temperature of 1000 C can transfer 30% ofits energy to the surrounding ambient radiatively and dissipate greaterthan 0.25 watts/cm2 of surface area. A similar naturally convectivelycooled surface with a surface temperature of 1500 C can transfer 35% ofthe heat radiatively and dissipate greater than 0.4 watts/cm2. Giventhat solid state light sources can approach 50% electrical to opticalconversion efficiency and that the typical spectral conversion is 300lumens/optical watt, using this approach a self cooling solid statelight source can emit 75 lumens for every 1.0 cm2 of light sourcesurface area. As an example, a ¼ inch×½ inch×2 mm thick self coolinglight stick can generate more than 150 lumens while maintaining asurface temperature less than 1000 C. The typical LED junctiontemperature for high powered devices can be over 1200 C and stillmaintain excellent life and efficiency. For surfaces with temperaturesless than 1200 C, the majority of the radiated energy is in the infraredwith a wavelength greater than 8 microns. As such, high emissivitycoatings, materials, and surfaces which are substantially transparent inthe visible spectrum are preferred embodiments of self cooling lightsources.

The emissivity of the materials in the infrared varies between 0 and 1.Glass has an emissivity of approximately 0.95 while aluminum oxide maybe between 0.5 and 0.8. Organics such as polyimides can have fairly highemissivity in thick layers. This however will negatively affect thetransfer of heat due to the low thermal conductivity of organics. Assuch high thermal conductivity high emissivity materials and coating arepreferred. High emissivity/low visible absorption coatings are describedin J. R. Grammer, “Emissivity Coatings for Low-Temperature SpaceRadiators”, NASA Contract NAS 3-7630 (30 Sep. 1966). Various silicatesare disclosed with emissivity greater than 0.85 and absorptions lessthan 0.2.

In order to maximize heat transfer to the ambient atmosphere, the needexists for luminescent thermally conductive materials which caneffectively spread the heat generated by localized semiconductor andpassive devices (e.g. LEDs, drivers, controller, resistors, coils,inductors, caps etc.) to a larger surface area than the semiconductordie via thermal conduction and then efficiently transfer the heatgenerated to the ambient atmosphere via convection and radiation. At thesame time, these luminescent thermally conductive materials mustefficiently convert at least a portion of the LED emission to anotherportion of the visible spectrum to create a self cooling solid statelight source with high L/W efficiency and good color rendering.Conventional wavelength converters in both solid and powder form aresubstantially the same size as the LED die or semiconductor devices.This minimizes the volume of the luminescent material but localizes theheat generated within the luminescent element due to Stokes losses andother conversion losses. In present day solid state light sourcesapproximately 50% of the heat generated is within the luminescentmaterial. By using a thermally conductive luminescent element with lowdopant concentration which also acts as a waveguide to the excitationlight emitted by the LEDs the heat generated by the luminescentconversion losses can be spread out over a larger volume. In addition amore distributed light source can be generated rather localized pointsources as seen in conventional LED packages. In this manner the needfor addition diffusing and optical elements can be eliminated orminimized. As such the use of luminescent thermally conductive elementswith surface area greater than the semiconductor devices mounted on theluminescent elements is a preferred embodiment.

Heat generated within the LEDs and phosphor material in typical solidstate light sources is transferred via conduction means to a much largerheatsink usually made out of aluminum or copper. The temperaturedifference between the LED junction and heatsink can be 40 to 500 C. Thetemperature difference between ambient and heatsink temperature istypically very small given that significant temperature drop occurs fromthe LED junction and the heatsink surfaces. This small temperaturedifference not only eliminates most of the radiative cooling but alsorequires that the heatsink be fairly large and heavy to provide enoughsurface area to effectively cool the LEDs. The larger the heatsink, thelarger the temperature drop between the LED junction and the surface ofthe heatsink fins. For this reason, heatpipes and active cooling is usedto reduce either the temperature drop or increase the convective coolingsuch that a smaller heatsink volume can be used. In general, the addedweight of the heatsink and/or active cooling increases costs forshipping, installation, and in some cases poses a safety risk foroverhead applications.

Ideally, like incandescent, halogen, sodium, and fluorescent lightsources, the emitting surface of the solid-state light source would alsobe used to cool the source. Such a cooling source would have an emittingsurface that was very close to the temperature of the LED junctions tomaximize both convective and radiative cooling. The emitting surfaceshould be constructed of a material that exhibited sufficient thermalconductivity to allow for the heat from small but localized LED die tobe spread out over a sufficiently large enough area to effectively coolthe LEDs. In this invention this is accomplished by spreading the heatgenerated within the luminescent element out over a larger volume, usinga thermal conductivity luminescent element that spreads the heatgenerated in the semiconductor devices used via conduction over a largersurface area than the semiconductor devices, and maximizing theradiative and convective cooling by high emissivity coatings, increasedsurface area, and higher surface temperatures created by efficientcoupling of the heat to the surface of the self cooling light source.

As stated earlier, the need exists for non-flammable solid state lightsources. The techniques to reduce the fire hazard of organics not onlycan not meet Class 1 or Class A requirements due to flame spread andsmoke but also degrade optical properties of the materials. Thisdisclosure cites inorganic materials and their use in self cooling solidstate lights sources which are non-flammable. Not only do these lightsources not contribute to the spread of flames and increase smoke duringa fire they also enable the maintenance of a contiguous fire, acoustic,and aesthetic suspended ceiling by eliminating and/or reducing thenumber of breaks in the ceiling. The lightweight nature of the sourcesdefined by high lumens per gram allow for direct attachment, suspension,and embedding of the light sources on, from, or in the suspendedceiling. This allows for seismic certification with the suspendedceiling and eliminates the need for additional support wires. Theelimination of support wires enables the user within the office spacethe ability to change, alter, replace, or otherwise move the lighting asneeded. This is also enabled by the use of magnetic, clip and otherreleasable forms of electrical and physical connectors to the grid,ceiling tiles, or power grids attached to or embedded in to the gridand/or ceiling tiles.

The use of the ceiling tile outer layer or scrim to form recyclingcavities or depressions which can then be used in conjunction withself-cooling light sources wherein the emitting surface and coolingsurface is substantially the same is also disclosed. In general the selfcooling solid state light fixtures disclosed transfer the majority oftheir heat to the office space side not the plenum side because theemitting/cooling surface is directly exposed the ambient within theoffice space. Electrical and physical connections to drivers in theplenum space can occur via push pin connects, embedded traces, surfacetraces, and other interconnect means. In general, the use of thisapproach to create thin, lightweight solid state light sources whichaesthetically blend into suspended ceilings wherein the surface whichemits also provides the cooling for the light source is a preferredembodiment of this invention.

FIG. 1A depicts a prior art vertical LED die 3 mounted on a substrate 4.The vertical LED die 3 is typically coated with an inorganic/organicmatrix 7 comprising of phosphor powder such as, but not limited to,Ce:YAG in a silicone resin material. The wire bond 2 is used toelectrically connect vertical LED die 3 to interconnect 5, which is thencoated with the inorganic/organic matrix 7. The other side of verticalLED die 3 is contacting interconnect 6 usually via eutectic solder orconductive adhesives. A lens 1 is further attached to substrate 4 toenvironmentally seal the assembly, enhance light extraction fromvertical LED die 3, and modify the far field optical pattern of thelight emitted by the device. In this case, emitted rays 9 aresubstantially traveling in the opposite direction of the heat ray 8.

As shown in the thermal schematic in FIG. 1A, cooling of theinorganic/organic matrix 7 occurs almost exclusively via thermalconduction through the vertical LED die 3 and into the substrate 4 viainterconnect 6. The heat generated within inorganic/organic matrix 7 dueto Stokes losses and scattering absorption is thermally conducted to thevertical LED die 3 at a rate determined by the thermal resistancedetermined by the bulk thermal conductivity of the inorganic/organicmatrix 7. As shown in the simplified thermal schematic, the averagetemperature of the inorganic/organic matrix 7 is determined by thethermal resistance R (phosphor/encapsulant) and T2 the averagetemperature of the vertical LED die 3. In order for heat generatedwithin the inorganic/organic matrix 7 to be dissipated to the ambient,it must move the thermal resistance of LED die 3 (RLED) and substrate 4(RPackage) before it can be dissipated to the ambient. This is asimplified thermal schematic which lumps bulk and interface thermalresistances and spatial variations within the device. But in general,heat generated within the inorganic/organic matrix 7 must be dissipatedmainly through the vertical LED die 3 due to low thermal conductivity ofthe other materials (e.g. Lens) which surround inorganic/organic matrix7. Additional heatsinking means can further increase the surface areausing metal, composite, or ceramic elements to enhance the dissipationof heat to ambient but the flow of heat is still basically the same. Thelens 1 acts as an extraction element for the emitted light rays 9 butalso acts as a barrier to thermal rays 8. Typically constructed ofsilicone or epoxy resins with thermal conductivity less than 0.1 W/mK,Lens 1 acts as a thermal insulator. Lens 1 also can limit thermalradiation from vertical LED 3 and inorganic/organic matrix 7 due to lowemissivity. In general this design requires that approximate 50% of theisotropic emission from the active region within vertical LED 1 must bereflected off some surface within the device and that the far fieldoutput of the device be substantially directional or lambertian innature. Even with the use of highly reflective layers, this represents aloss mechanism for this approach. These extra losses are associated withthe added pathlength that the optical rays must go through and multiplereflections off the back electrodes. This added pathlength andreflections, which are required to extract the light generated in theactive region of vertical LED 1, fundamentally reduces the efficiency ofthe LED based on the absorption losses of the LED itself. A significantportion of the light generated within the inorganic/organic matrix 7must also pass through and be reflected by vertical LED 1. Sincevertical LED 1 is not a lossless reflector, the added pathlength ofthese optical rays also reduce overall efficiency.

FIG. 1B depicts a prior artchip mounted LED 15. Solder orthermocompression bonding attaches flip chip mounted LED 15 via contacts16 and 21 to interconnects 17 and 18 respectively on substrate 19.Luminescent converter 14 may be an inorganic/organic matrix as discussedin FIG. 1A or solid luminescent element such as a Ce:YAG ceramic, singlecrystalline Ce:YAG, polycrystalline Ce:YAG or other solid luminescentmaterials as known in the art. In either case, the same coolingdeficiency applies with this design. Virtually all the cooling of theluminescent converter 14 must be through the flip chip mounted LED 15.Again, emission rays 12 travel in a direction substantially opposite tothermal rays 13 and once again approximately 50% the isotropic emissionof the active region of the flip chip mounted LED 15 must to redirectedwithin the device requiring the use of expensive metals like Ag,specialized coating methods and even nanolithography as in the case ofphotonic crystals.

The formation of contacts which are both highly reflective over a largeportion of the LED die area and still forms a low resistivity contacthas been a major challenge for the industry due to reflectivitydegradation of Ag at the temperature typically required to form a goodohmic contact. This high light reflectivity and low electricalresistivity leads to added expense and efficiency losses. Because boththe contacts must be done from one side typically an underfill 20 isused to fill in the voids created by the use of flip chip contacts. Lens11 forms a barrier to heat flow out of the device from both convectivelyand radiatively. The luminescent converter 14 is typically attachedafter the flip chip mounted die 15 is mounted and interconnected tosubstrate 19. A bonding layer 23 between the flip chip mounted die 15and luminescent element 14 further thermally isolates the luminescentelement 14. Typically, InGaN power LED UV/Blue chips exhibitefficiencies approaching 60% while White InGaN power LED packages aretypically 40%. The loss within the luminescent converter 14 thereforerepresents a substantial portion of the total losses within the device.In the case of an inorganic/organic matrix luminescent converter of FIG.1A, the conversion losses are further localized within the individualphosphor powders due to the low thermal conductivity of the silicone orepoxy matrix. The solid luminescent converter 14 has more lateralspreading due to the higher thermal conductivity of the solid material.Both cases are typically Cerium doped YAG with an intrinsic thermalconductivity of 14 W/mK. However since the silicone matrix has a thermalconductivity less than 0.1 W/mK and surrounds substantially all thephosphor powders, the inorganic/organic matrix has a macro thermalconductivity roughly equivalent to the silicone or epoxy by itself. Veryhigh loading levels of phosphor powder can be used but lead toefficiency losses due to higher scatter.

There is simply nowhere for the heat generated in luminescent converter14 to go except be thermally conducted into the flip chip mounted LED 15via the bonding layer 23. In most cases, solid luminescent converters 14must have an additional leakage coating 22 that deals with blue lightthat leaks out of the edge of the flip chip mounted LED 15. Aninorganic/organic matrix suffers from the same issues in FIG. 1A. Inboth FIGS. 1A and 1B, the emission surfaces are substantially differentfrom the cooling surfaces. The thermal schematic for FIG. 1B is similarto FIG. 1A in that heat generated within the luminescent converter 14 issubstantially dissipated through the flip chip mounted LED 15. With theadvent of high powered LEDs, a substantially portion of the heatgenerated within the device can be localized within luminescentconverter 14. This localization has led to a variety of solutionsincluding the use of remote phosphors. In general, luminescent converter14 efficiency reduces as its average temperature T4 increases. In theprior art the luminescent converter 14 dissipates the majority of itsheat through the flip chip mounted LED 15 with an average temperature ofT5. This is an inherently higher temperature than the ambient. The needexists for techniques whereby the heat generated within luminescentconverter 14 can be reduced for higher efficiency devices.

FIG. 2A depicts a vertical LED 24 of the present invention in which theoptical emission rays 26 travel substantially in the same direction asthe thermal rays 27. A thermally conductive luminescent element 25provides wavelength conversion for at least a portion of the lightemitted by vertical LED 24 and acts as an optical and thermal spreadingelement, extraction means, and a substrate for the electricalinterconnect. In FIG. 2A, overcoat 30 may be reflective, transparent,partially reflective and exhibit reflectivity which is wavelength and/orpolarization dependent.

Wire bond 29 connects interconnect 28 to contact pad 33 with contact 34attached via conductive ink or eutectic solder to interconnect 31. Atransparent/translucent bonding layer 32 maximizes optical and thermalcoupling into thermally conductive luminescent element 25 and eventuallyout of the device. The transparent/translucent bonding layer 32 maycomprise, but is not limited to, glass fit, polysiloxane, polysilazane,silicone, and other transparent/translucent adhesive materials.Transparent/translucent bonding layer 32 has a thermal conductivitygreater than 0.1 W/mK and even more preferably greater than 1 W/mK.Thermally conductive luminescent element 25 may comprise, but is notlimited to, single crystal luminescent materials, polycrystallineluminescent materials, amorphous luminescent materials, thermallyconductive transparent/translucent materials such as Sapphire, TPA,Nitrides, Spinel, cubic zirconia, quartz, and glass coated with athermally conductive luminescent coating, and composites of thermallyconductive transparent/translucent material and thermally conductiveluminescent materials.

In FIG. 2A a high emissivity layer 35 may be applied to the thermallyconductive luminescent element 25 to enhance radiative cooling. Inaddition, high emissivity layer 35 may also provide enhanced extractionefficiency by acting as an index matching layer between the surroundingair and the thermally conductive luminescent element 25, especially inthe case where extraction elements are used to increase extraction fromthe thermally conductive luminescent element 25. Unlike the previousprior art thermal schematic, the flow of heat generated in the thermallyconductive luminescent element 25 is directly coupled to the ambient viaconvective and radiative cooling off the surface of the thermallyconductive luminescent element 25 itself. This direct coupling approachcan only be effectively accomplished if the bulk thermal conductivity ofthe thermally conductive luminescent element 25 is high enough toeffectively spread the heat out over an area sufficiently large enoughto effective transfer the heat to the surrounding ambient. As such, athermally conductive luminescent element has a surface area greater thanthe attached LED with an average bulk thermal conductivity greater than1 W/mK wherein the heat generated within the Vertical LED 24 andthermally conductive luminescent element 25 are substantiallytransferred to the surrounding ambient via convection and radiation offthe surface of thermally conductive luminescent element 25. Highemissivity layer 35 most preferably has an emissivity greater than 0.8at 1000 C and an absorption less than 0.2 throughout the visiblespectrum. Alternately, the emissivity of the thermally conductiveluminescent element 25 may be greater than 0.8 at 1000 C and haveabsorption less than 0.2 throughout the visible spectrum.

FIG. 2B depicts a flip chip mounted LED 36 mounted on thermallyconductive luminescent element 42 via a transparent/translucent bondinglayer 43 and electrically connected via contacts 41 and 40 tointerconnects 44 and 45 on thermally conductive luminescent element 25.Interconnects 44 and 45 are thick film silver conductors formed viascreen printing, inkjet printing, lithographic means, or combinations ofthese other methods. As an example, thermally conductive luminescentelement 42 may contain a laser cut trench approximately 5 micron deepinto which silver paste is screen printed and fired. The surface ofconductive luminescent element 42 is then optionally lapped to create asmooth surface for interconnect 44 and 45. The resulting surface is nowsmooth enough for thermo compression bonded die, direct die attach diewith integral eutectic solders, and other direct attach bonding methods.Interconnects 44 and 45 are typically fired at a temperature greaterthan 4000 C. Interconnects 44 and 45 are thick film or inkjet silvertraces with line widths less than or greater than the width of the flipchip mounted LED 36. Optical losses within the device can be minimizedby minimizing the amount of silver used, minimizing the width of theinterconnect traces and maximizing the reflectivity of the silvertraces. Alternately, the thermal resistance between flip chip mountedLED 36 and the thermally conductive luminescent element 42 may beminimized by increasing amount of silver thickness or area. Overcoat 37may comprise, but is not limited to, glass frit, polysiloxane,polysilazanes, flame sprayed ceramics, and evaporative/CVD coatings. Ahighly reflective layer in overcoat 37 is optional. In this manner, acompact directional light source can be formed. Transparent/translucentbonding layer acts as an environmental and shorting barrier for thedevice. The reflector in overcoat 37 can be applied after all the hightemperature processing thereby maximizing reflectivity of the layer. Thethermal schematic shown in FIG. 2B again shows that there is a muchdifferent thermal conduction path than FIG. 1 devices. Thermallyconductive luminescent element 42 provides the cooling surfaces for thedevice as well as conversion of light from LED 36. The emitting surfaceof the device is also the cooling surface of the device.

FIG. 2C depicts a lateral LED 53 mounted onto thermally conductiveluminescent element 46. As in FIG. 2A and FIG. 2B, the optical emission50 and thermal rays 51 travel in substantially the same direction. Inthis configuration, a transparent/translucent overcoat 48 couplesthermal rays 56 and optical emission 57 out the backside of the device.Optical emission 50 and optical emission 57 may be the same or differentfrom each other regarding emission spectrum, intensity, or polarization.Additives, coatings, and combinations of both can affect the emissionspectrum, intensity and polarization within overcoat 48. Interconnect 49and 54 may comprise, but are not limited to, electrically conductivematerials in a dielectric matrix. A silver flake thick film paste screencan be printed and fired at greater than 4000 C with a reflectivitygreater than 50% to form an electrically conductive material in adielectric matrix. Wire bond 47 and 52 connect LED contacts 56 and 55 tointerconnect 49 and 54 respectively. Gold wire is preferred but the wirebond can be silver, silver coated gold, and aluminum in wire, foil, andtape form. The thermal schematic illustrates the flow of heat throughthe device to ambient. Transparent/translucent overcoat 48 may alsocontain luminescent materials. As an example, transparent/translucentovercoat 48 may comprise inorganic/organic matrix material such as butnot limited to HT 1500 Polysilazane (Clariant Inc.) containing at leastone luminescent materials such as, but not limited to, Eljen EJ-284fluorescent dye for conversion of green and yellow emission into red.Luminescent coatings can be applied via dip coating, spraying, inkjet,and other deposition techniques to form transparent/translucent overcoat48 on a light emitting device containing at least one thermallyconductive luminescent element 46.

FIG. 3A depicts a self cooling light source comprising of a singlethermally conductive luminescent element 60 attached both thermally andoptically onto at least one LED 61. LED 61 may comprise InGaN, GaN,AlGaN, AlinGaP, ZnO, AN, and diamond based light emitting diodes. Bothblue and red light emitting diodes such as, but not limited to, InGaNand AlinGaP LEDs are attached optically and thermally to at least onethermally conductive luminescent element 60. Heat 59 and emission 58generated by the LED 61 and the thermally conductive luminescent element60 are spread out over a substantially larger area and volume than theLED 61. In this manner the heat generated can be effectively transferredto the surrounding ambient.

Ce:YAG in single crystal, polycrystalline, ceramic, and flame sprayedforms are preferred materials choices for thermally conductiveluminescent element 60. Various alloys and dopants may also be usedcomprising of but not limited to gadolinium, gallium, and terbium. Thethermally conductive luminescent element 60 can be single crystal ceriumdoped YAG grown via EFG with a cerium dopant concentration between 0.02%and 2%, preferably between 0.02% and 0.2% with a thickness greater than500 microns. Alternatively, the thermally conductive luminescent element60 can be flamesprayed Ce:YAG with an optional post annealing. Thethermally conductive luminescent element 60 can be formed by flamespraying, HVOF, plasma spraying under a controlled atmosphere directlyonto the LED 61. This approach maximizes both thermal and opticalcoupling between the thermally conductive luminescent element and LED 61by directly bonding to LED 61 rather than using an intermediary materialto bond the LED 61 to thermally conductive luminescent element 60.Alternately, the thermally conductive luminescent element 60 maybeformed using at least one of the following methods; hot pressing, vacuumsintering, atmospheric sintering, spark plasma sintering, flamespraying, plasma spraying, hot isostatic pressing, cold isostaticpressing, forge sintering, laser fusion, plasma fusion, and other meltbased processes. Thermally conductive luminescent element 60 may besingle crystal, polycrystalline, amorphous, ceramic, or a meltedcomposite of inorganics. As an example, 100 grams alumina and Ce dopedYag powder which have been mixed together are placed into a container.The powders are melted together using a 2 Kw fiber laser to form amolten ball within the volume of the powder. In this manner the powderacts as the crucible for the molten ball eliminating any contaminationfrom the container walls. The use of the fiber laser allows forformation of the melt in approximately 4 seconds depending on the beamsize. While still in a molten state the ball may optionally be forgedbetween SiC platens into a plate. Most preferably the molten ball isgreater than 10 mm in diameter to allow sufficient working time as amolten material for secondary processing The plate may be furtherprocessed using vacuum sintering, atmospheric sintering, or hotisostatic pressing to form a translucent thermally conductiveluminescent element 60. The use of fiber laser based melt processing isa preferred method for the formation of luminescent oxides, nitrides,and oxynitrides as a method of reducing energy costs compared to hotpressing or vacuum sintering. The use of controlled atmospheresincluding vacuum, oxygen, hydrogen, argon, nitrogen, and ammonia duringthe laser based melting processes is disclosed. While fiber lasers arepreferred the use of localized actinic radiation to form a molten masswithin a powder mass to form thermally conductive luminescent element 60is disclosed.

FIG. 3B depicts a self cooling light source comprising of at least twothermally conductive luminescent elements 62 and 63 attached to at leastone LED 64. In this case, both thermal emission 64 and optical emission65 can be spread out and extracted from both sides of LED 64. In allcases, multiple LEDs allow for parallel, series, anti-parallel, andcombinations of all three with the appropriate electrical interconnect.In this case, optical emission 65 can be substantially similar ordifferent on the two sides of the devices. As an example, thermallyconductive luminescent element 62 can be 1 mm thick single crystal Cedoped YAG formed via EFG bottle which is then sliced into 19 mm.times.6mm wafers. The sliced surface enhances extraction of the Ce:YAG emissionout of the high index of refraction Ce:YAG material. Alternately,thermally conductive luminescent element 63 may be a pressed andsintered translucent polycrystalline alumina with a thermally fusedlayer of Mn doped Strontium Thiogallate and a layer of Eu dopedStrontium Calcium Sulfide within a glass frit matrix. In this manner, awide range of optical emission spectrums can be created.

In this particular case, the two sides of the devices will emit slightlydifferent spectrums. In general, unless an opaque reflector is placedbetween thermally conductive luminescent elements 62 and 63 there willbe significant spectral mixing within this device. This configurationcan be used for quarter lights, wall washers, chandeliers, and otherlight fixtures in which a substantial portion of the optical emission 65is required to occur in two separate directions. Directional elementssuch as BEF, microoptics, subwavelength elements, and photonicstructures impart more or less directionality to the optical emission 65of either thermal conductive luminescent elements 62 and/or 63.

In another example, Cerium doped YAG is formed via flame, HVOF, orplasma spraying and then optionally annealed, spark plasma sintered,microwave sintering, or HIP to improve its luminescent properties forone or both thermally conductive luminescent element 62 and/or 63. Atleast one InGaN LED and at least one AlInGaP LEDs are used for at leastone LED 64.

In yet another example, high purity aluminum oxide is flamesprayeddirectly onto at least one LED die 64 for thermally conductiveluminescent element 62 forming a translucent reflector. The emissivityof flame sprayed aluminum oxide is typically 0.8 allowing for enhancedradiative cooling from that surface. Thermally conductive luminescentelement 63 is single crystal Ce:YAG formed via skull melting and slicedinto 0.7 mm thick wafers 0.5 inch×1 inch in area with a cerium dopingconcentration between 0.1% and 2%. In this case, thermally conductiveluminescent element 62 does not necessarily contain a luminescentmaterial but acts as diffuse reflector and thermal spreading element forthe heat generated by both LED 64 and thermally conductive luminescentelement 62. By embedding LED 64 directly into thermally conductiveluminescent element 62 it is possible to eliminate pick and place, dieattachment processes and materials, and maximize both thermal transfer64 and optical emission 65 by eliminating unnecessary interfaces.Additional luminescent materials and opaque reflectors can be positionedwithin or coating onto either thermally conductive luminescent elements62 or 63. Pockets or embedded die can recess the die such that printingtechniques including but not limited to inkjet, silkscreen printing,syringe dispensing, and lithographic means.

FIG. 3C depicts two thermally conductive luminescent elements 72 and 74providing thermal conduction paths 74 and 79 to additional cooling means71 and 73. In this case, thermally conductive luminescent elements 72and 74 allow for thermal emission 76 and optical emission 77 and alsoprovide for thermal conduction paths 74 and 79. Additional cooling means71 and 73 may also provide for electrical connection to LED 75 viainterconnect means previously disclosed in FIG. 2. One or moreadditional cooling means 71 and 73 further enhance the amount of heatthat can be dissipated by the device. As an example, a typical naturalconvection coefficient is 20 W/m2/K and Ce:YAG has an emissivity of 0.8near room temperature. A self cooling light source comprising of two ¼inch×½ inch×1 mm thick pieces of Ce:YAG 72 and 74 with four directattach LEDs 75 soldered on silver thick film interconnect traces has asurface area of approximately 2.3 cm2. Using natural convection andradiative cooling approximately 500 milliwatts of heat can be dissipatedoff the surface of the self cooling light source if the surfacetemperature is approximately 1000 C and the ambient is 250 C and theemissivity is 0.8. Of the 500 milliwatts, 350 milliwatts of heat isdissipated via natural convection cooling and 150 milliwatts aredissipated via radiation. A typical 4000K spectrum output has an opticalefficiency of 300 lumens per optical watt. If the solid state lightsource has a electrical to optical conversion efficiency of 50%, 500milliwatts of optical output is generated for every 500 milliwatts ofheat generated. Under these conditions a ¼ inch×½ inch solid state lightsource operating with a surface temperature of approximately 1000 C canoutput 150 lumens without the need for additional heatsinking means.

The use of additional cooling means 71 and 73 can be used tosignificantly increase this output level by increase the surface areathat heat can be convectively and radiatively transferred to theambient. As is easily seen in the example, increasing the surface areais directly proportional to amount of heat that can be dissipated. It isalso clear that the electrical to optical conversion efficiencydramatically affects the amount of heat generated, which is a keyattribute of this invention. Unlike conventional LED packages lightgenerated within this self cooling solid state light source is extractedout of both sides of the device. Isotropic extraction as shown has a 20%theoretical higher efficiency than lambertian extraction. Also usingthis approach, the temperature difference between the LED 75 junctionand the surfaces of thermally conductive luminescent elements 72 and 74can be very low if the thermal conductivity is greater than 10 W/mK andthe LEDs 75 are attached such that there is low thermal resistance tothe surrounding thermally conductive luminescent elements 72 and 74. Inaddition, cooling means 71 and 73 may be physically different to allowfor the device to connect to different external power sources correctly.As an example, cooling mean 71 may be a pin and cooling means 73 maybe asocket such that a keyed electrical interconnect is formed. Alternately,cooling means 71 and 73 may contain magnets, which allow for attachmentof external power sources. Even more preferably the magnets havedifferent polarity such that a keyed interconnect can be formed.Additional cooling means 71 and 73 may include, but are not limited to,heatpipes, metals, glass, ceramics, boron nitride fibers, carbon fibers,pyrolytic graphite films, and thermally conductive composities. As anexample, boron nitride nano tubes fibers, as provided by BNNT Inc., arepressed with exfoliated boron nitride flakes to form and thermallyinterconnected skeleton matrix using pressing, cold isostatic pressing,warm isostatic pressing, and/or hot isostatic pressing to form a solidsheet. The boron nitride nanotube fibers interconnect the boron nitrideflakes and bond to the surface of the boron nitride flakes such that acontinuous thermal matrix is formed. The resultant skeleton matrix maythen be infused with polymeric or polymeric ceramic precursors includingbut not limited to polysilazane, polysiloxane, glasses, silicones, andother polymeric materials to form a composite.

Alternatively, The boron nitride nano tube fibers may be foamed into ayarn and woven into a cloth or felt and then infused with to form athermally conductive composite. Alternately, high thermal conductivitycarbon fibers and films may be used but boron nitride is preferred dueto its low optical absorption compared to carbon based approaches.Alternately, carbon based additional cooling means 71 and 73 may includea reflective layer to reduced absorption losses and redirect light fromthe source as well as provide additional cooling. Additional coolingmeans 71 and 73 may also diffuse, reflect, or absorb optical emission 77emitting between or from the adjacent edge of thermally conductiveluminescent element 72 or 74. In this manner the far field emission ofthe device can be adjusted both from an intensity and spectralstandpoint. Doubling the surface cooling area using additional coolingmeans 71 and 73 approximately doubles the lumen output as long as thethermal resistance of the additional cooling means 71 and 73 is low.

FIG. 4A depicts at least one LED 85 embedded within thermally conductiveluminescent element 83. Thermally conductive luminescent element 83 maybe formed via press sintering of aluminum oxide as known in the art toform a translucent polycrystalline alumina TPA with depressionssufficiently deep enough to allow for LED 85 to be recessed. Luminescentcoating 84 may be substantially only in the pocket formed in thermallyconductive luminescent element 83 or may cover substantially all thesurfaces of thermally conductive luminescent element 83. Alternately,single crystal, polycrystalline or amorphous phosphor, pieces, plates,rods and particles can be fused or bonded into or onto thermallyconductive luminescent element 83. In this manner, the quantity ofluminescent material can be minimized while maintaining high thermalconductivity for the thermally conductive luminescent element 81.

As an example, single crystal Ce:YAG pieces 1 mm×1 mm and 300 micronsthick can be fusion bonded into 1.1 mm×1.1 mm×500 micron deep pocketsformed into TPA press sintered plates and then fired at 17000 C in avacuum for 10 hours such that the single crystal YAG pieces are opticaland thermally fused into the bottom of the TPA pockets. LED 85 can thenbe bonded into the remaining depth of pocket and be used to excite thesingle crystal Ce:YAG pieces locally. The combined optical emission fromLED 85 and the single crystal Ce:YAG pieces would be spread out andextracted by the sinter pressed TPA while still maintaining high thermalconductivity.

Alternately, luminescent powders in glass frits, polysiloxane,polysilazane, and other transparent binders can be utilized inluminescent coating 84. In particular, high temperature binders inluminescent coating 84 such as polysilazane with luminescent powders,flakes, rods, fibers and in combination both pre-cured and as a bondingagent can be positioned between thermally conductive luminescent element83 and at least one LED 85.

Materials with high visible spectrum transmission, lower refractiveindex, high thermal conductivity, and low processing costs for net andfinal shape are preferred materials for thermally conductive luminescentelement 83. These materials include, but are not limited to, TPA,Spinel, Quartz, Glass, ZnS, ZnSe, ZnO, MgO, AlON, ALN, BN, Diamond, andCubic Zirconia. In particular, Spinel and TPA formed via press sinteringare low cost of manufacture of net shape parts. The use of techniquesused to form TPA parts as seen in transparent dental braces as known inthe art with luminescent elements either as coatings or bonded elementscan create thermally conductive luminescent element 83.

With LED 85 recessed into thermally conductive luminescent element 83,printing and lithographic methods can be used to electricallyinterconnect at least one LED 83 to outside power sources and/or otherLEDs or devices. Unlike wirebonding, this approach creates a low profilemethod of interconnecting LEDs, which eases assembly of multiple sticksand reduces costs.

In one example, LED 85 is bonded into a pocket formed via laser ablationin a 1 mm thick wafer of Spinel to form thermally conductive luminescentelement 83. In this example the Spinel may or may not includeluminescent elements or properties. The majority of the wavelengthconversion instead occurs locally around LED 85 via luminescent coating84 and/or additional luminescent coating 82. This minimizes the amountof luminescent material necessary yet still allows for a low thermalresistance to ambient for the luminescent materials. While only a singleside is shown in FIG. 4, the light source may also be bonded to anotherlight source, heatsink, another transparent/translucent thermallyconductive element to further enhance cooling and optical distributionfrom LED 85 and any luminescent elements within the light source. LED 85is bonded into the pocket using polysilazane containing 0.1% to 2% dopedCe:YAG powder with a particle size below 10 microns.

Transparent/translucent dielectric layer 81 is inkjet-printed over atleast one LED 85 except contact pads 87 and 86. In the case where LED 85uses TCO based contacts, at least a portion of the TCO is not covered bytransparent/translucent dielectric 81 to allow for electrical contact.Optionally an additional luminescent coating 82 may be printed or formedon at least one LED 85 to allow for additional wavelength conversion andto create a more uniform spectral distribution from the device.Interconnects 80 and 88 may then be applied either before or aftercuring of transparent/translucent dielectric 81. Polysilazane,polysiloxane, glass frit, spin-on glasses, and organic coatings areexamples of transparent/translucent dielectric 81, preferably thecoatings can maintain transparency above 3000 C. Formulations containingPolysilazane with and without luminescent elements are preferredmaterials for additional luminescent coating 82, transparent/translucentdielectric 82 and luminescent coating 84. Preferred luminescent elementsare powder phosphors, quantum dots, fluorescent dyes (example wavelengthshifting dyes from Eljen Technologies) and luminescent flakes andfibers.

Electrical connection to LED 85 is via interconnects 80 and 88 forlateral LED designs. Precision inkjet printing of silver conductive inksand/or screen printing of thick film silver inks form interconnects 80and 88. As an example thick film silver paste is screen printed andfired onto thermally conductive luminescent element 83 up to the pocketfor LED 85. Transparent/translucent dielectric 81 is inkjet printed suchthat only contacts 87 and 86 are left exposed and thetransparent/translucent dielectric 81 covers the rest of the exposedsurface of LED 85 and at least a portion of thermally conductiveluminescent element 83 in a manner to prevent shorting out LED 85 butstill allowing access to the thick film silver paste conductors appliedearlier. After or before curing of transparent/translucent dielectric 81and optionally additional luminescent coating 82, conductive ink isinkjet-printed connecting the thick film silver conductor appliedpreviously to the contacts 86 and 87. Using this approach, alignmentissues can be overcome due to the availability of inkjet systems withimage recognition and alignment features while still allowing for lowresistance conductors. In general, while inkjet printing of conductorscan be very accurate and be printed with line widths under 50 microns,the thickness is typically limited to under 10 microns which limits thecurrent carry capacity of long lines. Using this approach, thick filmsilver conductors which can be over 50 microns thick can be used tocarry the majority of the current and then short inkjet-printed tracescan be used to stitch connect between the thick film silver conductorsand contacts 87 and 86. Using this approach, gold wire bonding can beeliminated.

A transparent/translucent overcoat 89 may be applied over at least aportion of interconnects 80 and 89 and/or transparent/translucentdielectric 81, additional luminescent coating 82, and thermallyconductive luminescent element 83 to environmentally and/or electricallyisolate the device. Protective barrier layers on LED die 85 can beformed during LED fabrication to facilitate or even eliminate the needfor transparent/translucent dielectric layer 81 and allow for directprinting of interconnect 89 and 88 onto contacts 87 and 86 respectively.Catalytic inks and/or immersion plating techniques allow for theformation of thicker/lower resistivity traces for interconnect 89 and88, eliminate the need for thick film printing and allow for the use ofinkjet printing for the entire interconnect. Preferred materials fortransparent/translucent overcoat 89 include but are not limited topolysilazane, polysiloxane, spin-on glasses, organics, glass frits, andflame, plasma, HVOF coatings. Planarization techniques based on spin-onglasses and/or CMP can be used for transparent/translucent overcoat 89.Luminescent elements including but not limited to powders, flakes,fibers, and quantum dots can be incorporated in transparent/translucentovercoat 89, transparent/translucent dielectric 81, and additionalluminescent coating 82. Luminescent elements may be spatially oruniformly dispersed in these layers.

FIG. 4B depicts a light source in which a luminescent layer 91 is formedon a transparent/translucent element 90 containing extraction elements.Transparent/translucent element 90 can be, but is not limited to, singlecrystalline materials such as sapphire, cubic zirconia, YAG (doped andundoped), ZnO, TAG (doped and undoped), quartz, GGG (doped and undoped),GaN (doped and undoped), AlN, oxynitrides (doped and undoped),orthosilicates (doped and undoped), ZnS (doped and undoped), ZnSe (dopedand undoped), and YAGG (doped and undoped), polycrystalline materials,and amorphous materials such as glass, ceramic YAG (doped and undoped),ALON, Spinel, and TPA. In general, single crystal materials grown viaverneuil, EFG, HEM, Czochralski, CVD, hydrothermal, skull, and epitaxialmeans can be the transparent/translucent element 90.

Luminescent layer 91 may be formed directly one transparent/translucentelement 90 or be formed separately and then bonded totransparent/translucent element 90. Flamespraying, plasma spraying, andHVOF techniques can form either or both luminescent layer 91 andtransparent/translucent element 90. The light source can have atransparent/translucent element 90 with an alpha less than 10 cm-1throughout the visible spectrum and a luminescent layer 91 containing atleast one luminescent element emitting between 400 nm and 1200 nm. Theluminescent layer 91 can exhibit a refractive index, which is not morethan 0.2 different than transparent/translucent element 90. LED 99 maybe InGaN, AlInGaP, ZnO, BN, Diamond, or combinations of InGaN, AlInGaP,ZnO, BN, or diamond.

Both InGaN and AlInGaP LEDs can be used for LED 99 combined with atransparent/translucent element 90 comprising of at least one of thefollowing materials; sapphire, Spinel, quartz, cubic zirconia, ALON,YAG, GGG, TPA, or ZnO and luminescent layer 91 and/or additionalluminescent layer 98 containing Ce doped YAG. An additional red phosphoremitting between 585 and 680 nm can be used within luminescent layer 91and/or additional luminescent layer 98. These elements form a selfcooling light source which emits an average color temperature between6500K and 1200K that lies substantially on the black body curve is apreferred embodiment of this invention. The self cooling light sourcecan emit an average color temperature between 4000K and 2000K than liessubstantially on the blackbody curve.

Multiple self cooling light sources can be used within a fixture,reflector, optic or luminaire such that color and intensity variationsare averaged out in the far field. Three or more self cooling lightsources within a fixture, reflector, optic or luminaire creates auniform illumination at a distance greater than 6 inches from thesources. Transparent/translucent dielectric layer 93 may be inkjetprinted, silk screen printed, formed via lithographic means and exhibitsan alpha less than 10 cm-1 throughout the visible spectrum. Interconnect95 and 94 may be printed using inkjet, silkscreen, template, orlithographic means. Catalytic inks and immersion plating techniquesincrease conductor thickness and thereby reduce resistivity. Silvertraces with a trace width less than 500 microns and a reflectivitygreater than 50% for interconnect 95 and 94 reduce absorption of thelight generated within the light source. Contacts 96 and 97 on LED 99may be on one side only as in lateral devices or comprise one topcontact and one side contact as previously disclosed in US PatentApplication 20060284190, commonly assigned and herein incorporated byreference.

FIG. 4C depicts a self-cooling light source with at least one verticalLED 100 mounted to or at least partially embedded in thermallyconductive luminescent element 103. Composite, layer, single crystal,polycrystalline, amorphous, and combinations as described previously canbe used for the thermally conductive luminescent element 103. In thisparticular example, one vertical LED 100 is mounted such thatinterconnect 101 and 102 may be printed via inkjet, silkscreening, orlithographic means directly on thermally conductive luminescent element103 and in contact with a side of vertical LED 100. This embodimenteliminates the need for an additional dielectric and allows for the useof vertical LED devices which inherently exhibit lower Vf than lateraldevices. A substrate free LED as described in US patent application20090140279 (commonly assigned and incorporated herein by reference) isa preferred embodiment for LED 100. Direct die attach and flip chipmounting configurations may also be used for LED 100. For the substratefree case, InGaN and/or AlinGaP vertical LED 100 has TCO contacts 104and 105 for LED 100 wherein the interconnects 101 and 102 are thick filmsilver inks which form ohmic contact to the adjacent TCO contact 104 and105. In this manner, absorption losses are minimized and the need forlithographic steps to fabricate LED 100 is eliminated or minimized. Aself cooling light source contains at least one vertical LED 100 withTCO contacts 104 and 105 connected via thick film silver traces forinterconnect 101 and 102 directly bonded to TCO contacts 104 and 105 ona thermally conductive luminescent element 103. Optionally, bondinglayer 106 may be used to mount, improve extraction, incorporateadditional luminescent materials or position LED 100 onto or withinthermally conductive luminescent element 103.

FIG. 5 depicts various shapes of thermally conductive luminescentelements. FIG. 5A depicts a substantially flat luminescent element 107.Thickness is a function of dopant concentration but typically thethickness ranges from 200 micron to 2 mm for a uniformly doped Ce dopedYAG with a Cerium doping concentration between 0.02% and 10%. In orderfor efficient thermal spreading to occur, the thermal conductivity ofthe thermally conductive luminescent element 107 needs to be greaterthan 1 W/mK to adequately handle average power densities greater than0.1 W/cm2 of surface area on luminescent element 107. If the thermalconductivity is to low there is insufficient thermal spreading of theheat generated within the device which decreases the ability of the flatluminescent element 107 to cool itself via natural convection andradiative means.

FIG. 5B depicts a non-flat (hemispheric) luminescent element 108. Inthis case, light extraction can be enhanced for those rays which arewaveguided within the higher refractive index of non-flat luminescentelement 108. In addition, far field intensity and wavelengthdistributions can be modified. Multiple smaller self cooling lightsources with the same or different shaped thermally conductiveluminescent elements create uniform or specific far field intensity andwavelength distributions. The extraction of light generated within amedium with a refractive index greater than air is restricted by totalinternal reflection per Snell's Law. Shaped luminescent elements 108 canbe used to reduce the average optical path length of optical raysrequired to escape the luminescent element 108. Since absorption lossesare directly proportional to the optical path length for a givenabsorption coefficient (alpha), reducing the average optical path lengthdirectly translates into reduced absorption losses. The spatial locationof where the optical rays are generated within luminescent element 108,the refractive index of luminescent element 108, absorption coefficient(alpha) of luminescent element 108, bulk and surface scattering withinand on luminescent element 108, and the geometry of luminescent element108 can all be modeled as known in the art to optimize the extractionefficiency.

FIG. 5C depicts a non-flat (curved) thermally conductive luminescentelement 109 with a substantially uniform thickness. In this mannerextraction can be enhanced by maintaining a uniform thickness ofluminescent material. Extrusion, pressing, molding, sawing, boring, andflamespraying techniques as known in the art may be used to fabricatevarious shapes of thermally conductive luminescent elements.

FIG. 5D depicts a non-flat (rectangular saw tooth) thermally conductiveluminescent element 110 with additional surface elements to enhanceconvection cooling and optionally to modify or homogenize the emissionoutput of the self-cooling light source. Extrusion, pressing, andmolding techniques may be used to form thermally conductive luminescentelement 110.

FIG. 6A depicts a partially embedded LED 108 within a depression inthermally conductive luminescent element 107 mounted via bonding layer109. The formation of the depression may be by laser machining, electronbeam machining, etching (both chemical and mechanical), plasma etching,molding, and machining means. Substrate-free LEDs may be used forpartially embedded LED 108 with a thickness less than 300 microns. Byembedding partially embedded LED 108 in thermally conductive wavelengthconversion element 107, the thermal resistance between the two elementscan be reduced which lowers the junction temperature of the LED for agiven drive level. Optionally, more of the emission from partiallyembedded LED into thermally conductive luminescent element 107 can becoupled thereby changing the color temperature of the self cooling lightsource.

FIG. 6B depicts at least one LED 112 bonded onto thermally conductiveluminescent element 110 via bonding layer 111. In this case, bondinglayer 111 should exhibit a thermal conductivity greater than 1 W/mK andan alpha less than 10 cm-1 for the emission wavelengths of LED 112.

FIG. 7 depicts various printed contacts for TCO contact based LEDs. FIG.7A depicts a vertical LED comprising of a top silver paste contact 113on TCO layer 114 on p layer 117. Active region 116 is between p layer117 and n layer 115 with n layer 115 covered with TCO contact 118 andbottom silver paste contact 119. A substrate free LED allows dual sidedgrowth of TCO contact layers 114 and 118 on substrate free LEDstructures comprising of p layer 117, active layer 116 and n layer 115.Thick film high temperature silver paste contacts 113 and 119 can beprinted on LEDs with TCO contacts 114 and 118 and fired at temperaturesgreater than 2000 C in various atmospheres to form a low opticalabsorption, low Vf, and substantially lithography free LED devices.

FIG. 7B depicts a lateral device with printed/inkjet-printed contacts120 and 125. In all cases, ohmic contact to the n layer may include ornot include an intermediary TCO layer to form reasonable ohmic contact.In FIG. 7B, TCO 122 is grown on p layer 123. Active layer 124 is betweenp layer 123 and n layer 125. TCO 122 is doped ZnO grown via CVD with aresistivity less than 0.003 ohm-cm and greater than 1000 Angstromsthick. Printed etch masks allow for etch of the step down to n layer125. As an example, an AlInGaP LED epi may be grown on GaAs. The wafercan be etched and patterned to form the lateral device having TCO 122 onthe p layer 123. Printed contacts 120 and 125 are formed on TCO 122 andn layer 125. Optionally an additional TCO layer maybe formed of n layer125 to further reduce Vf. The addition of a eutectic solder layer toprinted contact 120 and 125 to create a direct die attach die is alsodisclosed. In a preferred embodiment, the AlinGaP epi is removed viachemical etching using a sacrificial etching layer between the AlinGaPand GaAs substrate as known in the art. The resulting direct attach diemay be additionally wafer bonded to GaN substrates as disclosed in U.S.Pat. Nos. 7,592,637, 7,727,790, 8,017,415, 8,158,983, and 8,163,582, andUS Patent Applications Publication Nos. 20090140279 and 20100038656,commonly assigned as the present application and herein incorporated byreference.

FIG. 7C depicts a printed contact with a top contact 126 and sidecontacts 132 and 130. Again TCO 127 forms a low ohmic transparentcontact to p layer 128 and the active region 129 is between p layer 128and n layer 130. Side contacts 131 and 132 contact the side walls of nlayer 130. N layer 130 is greater than 10 microns of thickness. Evenmore preferably, the thickness of n layer 130 is greater than 50 micronsbut less than 250 microns.

FIG. 8 depicts various methods of changing the far field distribution ofsingle self cooling source. In FIG. 8A, the refractive indices,geometry, and spacing of the LEDs 136, the wavelength conversionelements 133 and 135, and the bonding material 137 will determine thefar field distribution of the source. The far field distribution isdetermined by where the optical rays exit, how much of the optical rays,the direction of the optical rays and the spectrum of optical rays thatexit a particular spatial point on the single self cooling source. FIG.8 illustrates various reflectors, scattering elements, and diffuserswhich modify where, how much, which way and the spectrum of the lightrays emitted from the source. One or more wavelength conversion elementsfor mounting LEDs 136 can be used although two wavelength conversionelements 133 and 135 are depicted. Multiple LEDs 136 can be mounted onone or more surface of the one wavelength conversion element 133. Basedon these parameters, radiation will be emitted from the structure orlight guided within the source. Additionally, edge element 134 may alsomodify the far field distribution out of the device. Edge element 134and bonding materials 137 may be translucent, transparent, opaque,and/or luminescent. Luminescent powders within a transparent matrix foredge element 134 and bonding materials 137 can modify the emissionspectrum as well as the far field intensity distribution.

FIG. 8B depicts a self cooling light source where the entire end of theself cooling light source is substantially covered with a scatteringelement 139 within a matrix 138. Additionally, scattering element 139and matrix 138 may extend to encompass not only edges of the selfcooling light source but also substantial portions of the other surfacesof the self cooling light source. In this manner, light emitted from allthe surface of the self cooling light source can be redirected to modifythe far field intensity distribution. Luminescent materials forscattering element 139 are excited by at least a portion of the spectrumemitted by the self cooling light source.

FIG. 8C depicts edge turning element 140 comprising of metal, diffusescatterer, dielectric mirror, and/or translucent material whereby atleast a portion of the light generated within the LED or wavelengthconversion elements are redirected as depicted in ray 141.

FIG. 8D depicts an outer coating 142 which may be translucent, partiallyopaque, polarized, and/or luminescent. The far field intensity,polarization, and wavelength distribution can be modified both in thenear field and far field and spatial information can be imparted ontothe self cooling light source. As an example, a self cooling lightsource with a shape similar to a candle flame may have a spectrallyvariable outer coating 142 such that red wavelengths are emitted morereadily near the tip of the candle flame and blue wavelengths areemitted more readily near the base of the candle flame. In this fashion,the spatially spectral characteristics of a candle flame could be moreclosely matched. Using this technique a wide range of decorative lightsources can be formed without the need for additional optical elements.

In another example, outer coating 142 may comprise a reflective coatingsuch as aluminum into which openings are etched or mechanically formed.More specifically, sunlight readable indicator lights can be formedusing this technique as warning, emergency, or cautionary indicators.The use of circular polarizers within outer coating 142 can enhancesunlight readability. Alternately, outer coating 142 could be patternedto depict a pedestrian crossing symbol that could be either directviewed or viewed through an external optic thereby creating a ultracompact warning sign for crosswalks and other traffic relatedapplications. In another example, outer coating 142 may comprisespectrally selective emissivity coating such that the emissivity of theself cooling light source is enhanced for wavelengths longer than 700nm. By enhancing the infrared and far infrared emissivity of the selfcooling light source more efficient light sources can be realized. Asstated in the previous example of FIG. 3 the radiation coolingrepresents a significant percentage of the cooling in self cooling lightsources. It is preferred that high emissivity coatings be used for outercoating 142 to maximize cooling from the surface of the self coolinglight source. Most preferred is an outer coating 142 with an emissivitygreater than 0.5. Depending on the maximum surface temperature theradiative cooling can represent between 20% and 50% of the heatdissipation of the source.

FIG. 9A depicts the use of die shaping of optical devices within a media143. As an example, LED 145 contains an active region 146 embeddedwithin media 143. Using ray tracing techniques known in the art, thereis an optimum angle 144 to maximize the amount of radiation transferredinto media 143. Typically, semiconductor materials exhibit highrefractive index which tends to lead to light trapping within the LED145. In FIG. 9A the optimum angle 144 subtends the active region 146 asshown in the figure.

Alternately, FIG. 9B depicts that surfaces 149, 148 and 147 may benon-orthogonal forming a non square or rectangular die. In both thesecases, light trapped within the LED 150 can more efficiently escape thedie. The use of both forms of die shaping together is preferred. The useof non-rectangular shapes for LED 150 embedded within a wavelengthconversion element to enhance extraction efficiency is a preferredembodiment of this invention.

FIG. 10A depicts different mounting methods for LEDs 152 and 154 withinwavelength conversion element 151 and the use of bonding layers 153 and155. Bonding layers 153 and 155 thermally, optically, and mechanicallyattach LEDs 152 and 154 to at least one surface of wavelength conversionelement 151. LED 152 is at least partially embedded within wavelengthconversion element 151 which can allow for both edge and surfacecoupling of radiation emitted by the LED 152 into wavelength conversionelement 151 using bonding layer 153. Alternately, LED 154 issubstantially coupled to the surface of wavelength conversion element151 using bonding layer 155. Bonding layers 55 and 153 may be eliminatedwhere wavelength conversion element 151 is directly bondable to LEDs 154and 152 using wafer boding, fusion bonding, or melt bonding.

FIG. 10B depicts a typical transmission spectrum 157 of wavelengthconversion elements. Blue emission 156 is absorbed by the wavelengthconversion element and then reemitted at longer wavelengths. Redemission 158 is typically not strongly absorbed and therefore behaves asif the wavelength conversion element 151 is simply a waveguide.Virtually any color light source can be realized by properly selectingthe right combination of blue and red LEDs within the wavelengthconversion element 151. While wavelength conversion is a preferredembodiment, FIG. 10B illustrates that self-cooling light sources do notrequire that the wavelength conversion element 151 be luminescent. Inthe case of a red self-cooling light source, wavelength conversionelement 151 may be used to optically distribute and thermally cool theLEDS without wavelength conversion. Alternately, UV responsiveluminescent materials can be used for wavelength conversion element 162with UV LEDs 164 or 165. The transmission spectrum 157 is shifted toshorter wavelength which allows for the formation of self cooling lightsources which exhibit white body colors, as seen in fluorescent lightsources. This wavelength shift however is offset by somewhat reducedefficiency due to larger Stokes shift losses.

FIG. 11 depicts a color tunable self-cooling light source containing atleast one wavelength conversion element 162 with an electricalinterconnect 168, at least one blue LED 164, at least one red LED 163,and drive electronics 165, 166, and 167. Electrical interconnect 168 isa thick film printed silver ink. Three separate pins 159, 160, and 161to provide independent control of blue led 164 from red LED 163. Pins159, 160, and 161 can be physically shaped to allow for keying therebyensuring that the self-cooling light source is properly connected toexternal power sources. While pins 159, 160 and 161 are substantiallyshown on the same side of wavelength conversion element 162, the use ofalternate pin configurations are anticipated by the inventors. Ingeneral, external electrical interconnect can be accomplished via pins159, 160, and 161 as shown in FIG. 11 or via alternate interconnectmeans including, but not limited to, flex circuits, rigid elementscontaining electrical traces, coaxial wires, shielded and unshieldedtwisted pairs, and edge type connectors on or connected to wavelengthconversion element 162 are embodiments of this invention. Additionallyfeedthroughs within wavelength conversion element 162 can be formed viamechanical, chemical etching, laser, waterjet, or other subtractivemeans to form external interconnects to any of the previous listedelectrical interconnect elements in any plane of the wavelengthconversion element 162.

Drive electronics 165, 166, and 167 may comprise both active and passiveelements ranging from resistors, caps, and inductors. In this manner, avariety of external drive inputs can be used to excite the light source.As an example, a current source chip may be mounted onto the wavelengthconversion element 162 and connected to an external voltage source viapins 159,160, and 161. As known in the art, typical current source chipscan also have an external resistor which sets the current which flowsthrough the current source chip. The external resistor may be mounted onthe wavelength conversion element 162 or be external to the source andconnected to current source chip via pins 159, 160, and 161. As thefunctionality within the light source increases, the number pins may beincreased. Integrated circuits can be used for drive electronics 165,166, and/or 167. Wavelength conversion element 162 also substantiallycools the drive electronics 165, 166, and 167 as well as LEDs 164 and165. Pins 159, 160, and 161 may be used to remove heat from the heatgenerating elements of the light source. Wavelength conversion element162 is luminescent and provides for optical diffusion and cooling of theheat generating elements within the self cooling light source In thiscase, additional wavelength emitters may be added including, but notlimited to, UV, violet, cyan, green, yellow, orange, deep red, andinfrared

FIG. 12 depicts a self cooling light source with an embedded activedriver 172 capable of driving multiple LEDs 171, all of which aremounted and cooled substantially by wavelength conversion element 169.Input pins 170 may provide power input to active driver 172 but alsoprovide outputs including, but not limited to, light source temperature,ambient temperature, light output levels, motion detection, infraredcommunication links, and dimming controls. As previously disclosed, thetransmission spectrum of the wavelength conversion element 169 allowsfor low absorption of longer wavelengths. An infrared/wireless emitterand receiver can be integrated into embedded active driver 172 so thatthe self cooling light source could also serve as a communication linkfor computers, TVs, wireless devices within a room, building, oroutside. This integration eliminates the need for additional wiring anddevices.

FIG. 13A depicts the use of electrical contacts 174 and 175 asadditional thermal conduction paths for extracting heat 178 out of thewavelength conversion elements 173 and 174 additionally cooling pathsfor LED 177. LED 177 may be direct attach or flip chip and may be alateral, vertical, or edge contact die. As an example, electricalcontact 174 and 175 may comprise 0.3 mm thick Tin plated aluminum platessandwiched between wavelength conversion elements 173 and 174. In thismanner both electrical input and additional cooling means for wavelengthconversion elements 173 and 174 as well as LED 177 can be realized.

FIG. 13B depicts a rod based light source with LEDs 180 within rodshaped wavelength conversion element 182 wherein heat 181 isadditionally extracted via conduction to contacts 178 and 179.Alternately, hemispherical, pyramidal, and other non-flat shapes andcross-sections maybe used for wavelength conversion element 182 tocreate a desired intensity, polarization, and wavelength distribution.Cross-section and other shapes, such as spheres and pyramids, maximizethe surface area to volume ratio, so that convective and radiativecooling off the surface of the wavelength conversion element 182 ismaximized while using the least amount of material possible. As anexample, contacts 178 and 179 may comprise 2 mm copper heatpipesthermally bonded via a bonding method including but not limited togluing, mechanical, soldering, or brazing means to wavelength conversionelement 182. In this manner additional cooling maybe realized. LEDs 180may be mounted on the surface or inside of wavelength conversion element182. As an example LEDs 180 may be mounted on the flat surface of twohemispherical wavelength conversion elements 182. The two hemisphericalwavelength conversion elements 182 are bonded together to form aspherical self cooling light source with the LEDs 180 embedded withinthe wavelength conversion elements 182.

Alternately, the LEDs 180 may be mounted on the spherical surface of thehemispherical wavelength conversion element 182 such the light generatedby LED 180 generally is coupled into the hemispherical wavelengthconversion element 182. Optionally, the flat surface of hemisphericalwavelength conversion 182 may have additional luminescent coatings suchthat the light emitted by LEDs 180 is effectively coupled by thehemispherical wavelength conversion element 182 onto the luminescentbonding layer which reflects, transmits, converts or otherwise emitsboth the light emitted by the LEDs 180 and any luminescent elements backout of the hemispherical wavelength conversion element 182. Theadvantage of this approach is that the LEDs 180 are mounted closer tothe cooling surface of the wavelength conversion element, a high degreeof mixing is possible, and the angular distribution of the source can becontrolled by how well the bonding layer is index matched to thewavelength conversion element 182. Bonding two hemispherical wavelengthconversion elements 182 together forms a spherical source withexternally mounted LEDs 180.

FIG. 14 depicts a self cooling light source with at least two thermallyand/or optically separated zones. Waveguide 183 containing LEDs 184 isoptically and/or thermally isolated via barrier 185 from waveguide 186and LEDs 187. Dual colored light sources can be formed. Alternately,temperature sensitive LEDs such as AlInGaP can be thermally isolatedfrom more temperature stable InGaN LEDs. Waveguide 183 and 186 may ormay not provide luminescent conversion. LEDs 184 are AlInGaP (red) LEDsmounted to waveguide 183 made out of sapphire. LEDs 187 are InGaN blueLEDs mounted onto waveguide 186 which is single crystal Ce:YAG. Thebarrier 185 is a low thermal conductivity alumina casting material.AlinGaP efficiency drops by 40% for junction temperatures over 600 Cwhile InGaN efficiency will drop only by 10% for a similar junctiontemperature. White light sources can be realized by thermally isolatingthe AlinGap from the InGaN high overall efficiency. Using this approachthe two sections operate at different surface temperatures. The InGaNLED 187 and waveguide 186 operates at a higher surface temperature whilethe AlInGaP LED 184 and waveguide 183 operates at a lower surfacetemperature.

FIG. 15 depicts Blue LED 189 mounted to wavelength conversion element188 and Red LED 192 with driver 190. Power lines 191, 193, 194, and 195and control line 196 are also shown. Red LED 192 drive level is set viacontrol line 196 by controlling the voltage/current flow available viapower line input 191 and output 195. Typically driver 190 would be aconstant current source or variable resistor controlled via control line196. As stated earlier, blue LED 189 is typically InGaN with more stableregarding temperature, life and drive levels than red LED 192 typicallyAlInGaP. As an example, TPA coated with europium doped strontiumthiogallate singularly or as a multiphase with another gallate, such asEu doped magnesium gallate for wavelength conversion element 188 isexcited by 450 nm LED 189. 615 nm AlinGaP red LED 192 is also mounted onthe wavelength conversion element 188 along with driver 190. Heat isspread out via wavelength conversion element 188 as well as theradiation emitted by blue LED 189 and red LED 192. Control line 196 isused to adjust the color temperature of the source within a range byincreasing the current to red LED 192 relative to the fixed output ofblue LED 189. Additional LEDs and other emission wavelengths can beused.

FIG. 16 depicts a white light spectrum for a typical solid state lightsource. FIG. 16A illustrates high color temperature low CRI spectrum 197typically created by blue LEDS and Ce:YAG phosphors. Additionalphosphors are typically added to add more red content in order to lowerthe color temperature as shown in spectrum 198. This red additionhowever requires that a portion of the blue and in some cases some ofthe green be absorbed which reduces overall efficiency.

FIG. 16B depicts the typical spectrum 199 from a blue LED, Ce:YAGphosphor, and red LED. The red LED spectrum is additive as shown inspectrum 200. In general, both methods of FIG. 16 are used to formself-cooling light source described in this invention.

FIG. 17 depicts a high CRI white light spectrum 201 formed by mixingphosphor and LED spectrums A, B, C, D, and E. Spectral ranges can bemixed, diffused and converted within the wavelength conversion elementsdisclosed in this invention in addition to cooling, mechanicallymounting, environmentally protecting, and electrically interconnectingthe devices needed to generate the spectrums depicted. As an example,spectrum B may be derived from a blue 440 nm emitting LED, a portionwhose output is used to excite a single crystal Ce:YAG luminescentelement as previously disclosed to form spectrum A between 500 nm and600 nm. Spectrum C may comprise a cyan quantum dot which also converts aportion of output of the blue 440 nm emitting LED into 490 to 500 nmwavelengths. Spectrum D maybe produced by using a wavelength shifter diesuch as Eljen-284 (Eljen Technologies Inc.) to convert a portion ofSpectrum A into wavelengths between 580 nm and 700 nm and Spectrum Emaybe a AlinGap red LED emitting between 600 and 800 nm. Infraredemitters or converters may also be added for communication links,security, and night vision applications.

FIG. 18 depicts various shapes of waveguides and luminescent coatings.FIG. 18A depicts a textured thermally conductive waveguide 203 with aluminescent coating 202. As an example, a micro lens array may be presssintered out of TPA and coated with Ce:YAG via flame spraying. FIG. 18Bdepicts an EFG formed single crystal Ce:YAG rod 204 coated with a highemissivity coating 205 with a refractive index substantially equal tothe geometric mean of Ce:YAG and air and a thickness greater than 300angstroms. In the previous example of FIG. 3 the importance of radiativecooling even at low surface temperatures is disclosed. In this examplethe radiative cooling can represent up to 30% of the total heatdissipated as long as the emissivity of the surface is above 0.8.Emissivity varies from very low (0.01) for polished metals to very high0.98 for carbon black surfaces. The use of high emissivity coatings 205that are also transparent in the visible spectrum are most preferred.These include but not limited to silicates, glasses, organics, nitrides,oxynitrides, and oxides. Even more preferred are high emissivitycoatings 205 that also exhibit a thermal conductivity greater than 1W/mK. The high emissivity coating 205 thickness is preferably between1000 angstroms and 5 microns thick. The emissivity coating 205 may alsobe luminescent.

FIG. 19A depicts a self cooling light source 206 and an optic 207. Optic207 may be reflective, transparent, translucent or opaque. Bothdecorative and directional means may be used as an optic. Parabolic,elliptical, non-imaging and other optical configuration as known in theart may be used as an optic. In particular, the use of prismatic surfaceelements on optic 207 wherein a substantial portion of the light emittedby self cooling light source 206 are redirected in a directionorthogonal to their original direction are embodiments of thisinvention. Optic 207 redirects a portion of the light from light source206 downward. The optic 207 may comprise, but is not limited to, glass,single crystal, polymer or other translucent/transparent materials.Colored translucent/transparent materials create a specific decorativeor functional appearance. As an example a light source 206 may beembedded into an orange glass glob to form a decorative lamp. Theelimination of the need for a heatsink greatly simplifies the opticaldesign and allows for a wider range of reflectors and optical elements.

Alternately, FIG. 19B depicts an external movable reflector 209 whichslides 210 up and down light source 208. Using this approach thepercentage of downward light can be adjusted relative to the amount ofdiffuse lighting. Again the elimination of heatsinks and the formationof an extended source greatly simplifies the optical design of the lightfixture.

FIG. 20 depicts methods of adjusting the far field distributions ofsingle light sources. In FIG. 20A, the far field distribution bothintensity and wavelength can be adjusted by mounting methods for theLEDs 214 and 216 within or onto wavelength conversion element 211. LED214 depicts an embedded LED 214 in which a pocket or depression isformed in wavelength conversion element 211. This embedded LED changesthe ratio of transmitted rays 212 to waveguided rays 213 relative tosurface mounted LED 216 which has a substantially different ratio oftransmitted rays 217 to waveguided rays 218.

In FIG. 20B an optic 220 extracts light off of more than one surface oflight source 219. In this case, rays 221 are redirected substantiallyorthogonally to the surface the rays were emitted from and mixed withthe rays from other surfaces of light source 219. The optic 220 may be aprism, lens, parabolic, elliptical, asperical, or free formed shape.

FIG. 20C depicts embedded LEDs 225 in embedded occlusions 226 withedge-turning elements 224 which were previously disclosed. Rays 227 and223 can be directed substantially orthogonally out of the wavelengthconversion element 222.

FIG. 21A depicts a LED die 230 bonded into a wavelength conversionelement containing depressions or pockets 228 using a bonding layer 229,a electrical interconnect layer 231 and protective dielectric layer 232.As an example, a 500 microns thick Ce:YAG single crystal wafer is laserdrilled to have a pocket into which lateral LED die 230 is placed andbonded using a polysilazane. The polysilizane is at least partiallycured. The polysilizane is further coated using inkjet printingtechniques to cover all but the metal contact pads of lateral LED die230. Conductive ink is printed via, but not limited to, inkjet,screenprinting, tampo, or lithographic means such that the exposed metalcontact pads of lateral LED die 230 are interconnected electrically viaelectrical interconnect layer 231. Nanosilver, silver paste, and otherhighly reflective printable electrically conductive inks, pastes orcoatings are the preferred conductive ink. A protective dielectric layer232 is applied via, but not limited to, inkjet, spin coating, dipcoating, slot coating, roll coating and evaporative coating means.

FIG. 21B depicts LED 233 mounted to the surface of waveguide 234 most ofthe rays do not couple to the waveguide efficiently. FIG. 21C depictsembedded LED 235 within a pocket in waveguide 236. Optically andthermally there is more coupling into waveguide 236. In addition the useof embedded LED 235 allows for simplified interconnect as depicted inFIG. 21A. Further luminescent insert 237 may be used to convert at leasta portion of the spectrum from LED 233 or 235. In this case lower costmaterials may be used for waveguide 234 and 236 respectively. As anexample, single crystal Ce:YAG inserts 50 microns thick with a Ce dopingconcentration greater than 0.2% with substantially the same area asembedded LED 235 can be inserted into press sintered TPA waveguides. Inthis manner, the amount of luminescent material can be minimized whilestill realizing the benefit of a thermally conductive element including,but not limited to, waveguide, increased thermal cooling surface, andoptical spreading of the light over an area larger than eitherluminescent insert 237 or LED 235. Ceramic, polycrystalline, amorphous,composite and pressed powders of luminescent materials may be used forluminescent insert 237. A waveguide 236 with a thermal conductivitygreater than 1 W/mK can work with a luminescent insert 237. LED 235comprises of one or more of the LED which is an InGaN, AlGaN, and/orAlInGaP based LED in waveguide 236 with a thermal conductivity greaterthan 1 W/mK with at least one luminescent insert 237.

FIG. 22 depicts a prior art LED light strip. Enclosure 2202 contains LEDpackages which typically comprise a submount 2208, LED die 2206, and anencapsulating lens 2204. The inside of enclosure 2202 is reflective thelight emitted by the LED die 2206 and a diffuser/lens element 2200 isplaced at distance sufficient for the light from the individual LEDpackages to mix and form a spatially uniform output on the outputsurface of the diffuser/lens element 2200. Heat is extracted from theLED packages through the enclosure 2202 to heatsink 2210. In general themajority of the heat generated travels in the opposite direction of thelight emission which is through diffuser/lens element 2200. From apractical standpoint the distance between the LED packages is theminimum distance the diffuser/lens element 2200 needs to be away fromthe LED packages to get uniformity. In this configuration thediffuser/lens element 2200 typically is typically made of organicmaterials (plastic) and even the enclosure 2202 and heatsink 2210 may befilled with organic materials. For example the diffuser/lens element2200 is typically acrylic or polycarbonate which is flammable underexposure to flame.

Unfortunately, the techniques known in the art to reduce flame spreadingand smoke adversely affect the optical transmission and opticalabsorption losses in these materials. This approach suffers from lowlumens per gram due the weight of the heatsink, typically less than 1lumen/gram. Because the majority of the light emitted by the LEDs inthis configuration is emanating from a point source, the LED 2206 of thelight source uniformity must be accomplished within the diffuser/lenselement 2200 in a single pass. The LEDs in these prior art light sourcesare directly viewable (imaged by the naked eye through the diffuser/lenselement) due to the short optical path length between the LED and thediffuser. Therefore, there is minimal light bounces or recycling beforeemission from the light source. Intensity, uniformity and wavelengthaveraging all suffer due to the lack of mixing and averaging. Also thethickness of the source must be increased to allow for mixing to occurwhen the LEDs are mounted in this direct view configuration. This makesit difficult to achieve aesthetically pleasing low profile lightsources.

FIG. 23 depicts a prior art solid state waveguide based panel light witha waveguide 2305 typically made of acrylic and polycarbonate. In thisconfiguration the amount of flammable material is even larger with up toseveral pounds of organic material that is used to form a largewaveguide as required in a 2 ft.×2 ft. or 2 ft.×4 ft troffer. Therequired optical properties such as transmission and low scatter orabsorption losses are even more strict in this configuration. This makesit very difficult to use conventional flame retardant techniques onthese elements. Light from the LED package 2313 is coupled to thewaveguide 2305 using a reflector 2308. Heat generated by the LED package2313 is dissipated by thermal conduction to appended heatsink 2310(typically an outer metal frame or bezel). A rear reflector 2304,extraction elements 2306, end reflector 2302, and top diffuser 2300 areused to direct light within the waveguide 2305 through the top diffuser2300. Typically reflectors and diffusers are all organic and furtherenhance the flammability and toxic smoke generation upon exposure toopen flames. In general, the use of large area organic materials infilms, diffusers, organic optical waveguides, organic reflective films,and organic elements within LED packages can pose an increased risk tofirefighters and occupants during a fire within a structure. Manyorganics like acrylic emit not only smoke but also toxic and noxiouschemicals when burned. The need exists for non-flammable solid statelight sources.

This invention overcomes all of the aforementioned deficiencies byindirectly mounting the LEDs within a light recycling cavity formed by areflector and an optically reflective and light transmitting thermallyconductive element which functions as a reflective exit aperture to thelight recycling cavity and simultaneously removes the heat generated bythe LEDs from the light emitting surface of the light transmittingthermally conductive element.

FIG. 24 depicts a non-flammable self cooling light source of the presentinvention in which the emitting and cooling surfaces are substantiallythe same. As an example, the light source contains at least one LED2414, at least one reflector element 2412, and at least one lighttransmitting thermally conductive element 2400. The at least one lighttransmitting thermally conductive element 2400 has at least one exteriorlight emitting surface. The at least one exterior light emitting surface2401 faces outward into the room or lighted area, while the interiorsurface 2403 of at least one light transmitting thermally conductiveelement 2400 faces into the light recycling cavity 2409 formed by the atleast one light transmitting thermally conductive element 2400 and atleast one reflector element 2412. The at least one LED 2414 is containedwithin the light recycling cavity 2409 and in thermal contact with saidat least one light transmitting thermally conductive element 2400 suchthat the heat from said at least one LED 2414 is transferred via thermalconduction from said at least one LED 2414 to the exterior lightemitting surfaces 2401 of said at least one light transmitting thermallyconductive element 2400 and wherein the heat is removed to ambient viaconvection and radiative cooling from the exterior light emittingsurfaces 2401 of the at least one light transmitting thermallyconductive element 2400.

The light transmitting thermally conductive element 2400 has a thermalconductivity that is greater than 1 W/mK. More preferably the lighttransmitting thermally conductive element 2400 has a thermalconductivity that is greater than 10 W/mK. Most preferably the lighttransmitting thermally conductive element 2400 has a thermalconductivity that is greater than 20 W/mK. In this particular embodimentat least one LED 2414 (this can be one of the following: a direct attachLED die, flip chip LED die, wire bonded LED die or other LED dieconfiguration with or without wavelength conversion layer 2416 or an LEDpackage with integrated wavelength conversion layer 2416) is soldered,wirebonded, adhesively bonded or mechanically attached to at least onelight transmitting thermally conductive element 2400 either via or inaddition to being attached to interconnect 2402 (which is comprised ofat least one electrically conductive trace printed and fired on lighttransmitting thermally conductive element 2400). This electricalconductive interconnect is preferably highly reflective or lighttransparent. Interconnect 2402 may be conductive inks containing silverwith either organic or inorganic binders. The binders are removed duringfiring resulting in a metal trace. Light transmitting thermallyconductive element 2400 is typically composed of inorganic materialssuch as but not limited to alumina, sapphire, Yag, GGG, Spinel, andother inorganic high thermal conductivity materials which exhibit lightabsorption losses below 1 cm-1 throughout the visible wavelength range,a thermal conductivity greater than 1 W/mK, and are non-flammable whenexposed to a flame. Alternately, glass composites and non-flammableinorganic/organic composites may be used such as polysilazane/hBN.Polysilazane as well as other siloxanes may be used based on theirtendency to convert to non-flammable residues upon exposure to flames.Alumina is preferred due to its ready availability in thin layers, lowcost, and compatibility with high temperature process like sintering ofconductive inks and soldering. Alumina has a thermal conductivity ofgreater than 20 Watt/m-K.

Whereas materials with high light transmissivity (TPA, Spinel, sapphire,etc.) may be used as the light transmissive thermally conductive element2400, these materials are relatively expensive. Lower cost ceramics tendto be more opaque and have low light transmission and higherreflectivity. However, it has been found by practicing the tenets ofthis invention that high net light extraction efficiency may be achievedwith these materials. For example commercial grade Alumina (96% Al2O3)500 micrometers thick has an optical transmission of less than 16% witha reflectivity of 84%. Visually it has a white body and appears opaque.However, by utilizing this highly reflective material (e.g. alumina) asthe light transmitting thermally conductive element and forming a lightrecycling cavity 2409 with reflector 2412 greater than 70% of the lightmay be extracted from the light recycling cavity. Using these morereflective (84%) materials, light emitted from the LED(s) 2414 andoptionally wavelength converted, impinges on the reflector 2412 of thelight recycling cavity 2409 and is reflected 2422 to the lighttransmitting thermally conductive element 2400 where 16% would betransmitted and emitted 2424 from the outside surface 2401 of lighttransmitting thermally conductive element 2400. However, the light nottransmitted (84%) is reflected 2426 back to the reflector 2412 where itagain is reflected back to the light transmitting thermally conductiveelement 2400 and ˜13.4% (16% of the 84% reflected light) is transmittedthrough and emitted 2428 from the outside surface 2401 of lighttransmitting thermally conductive element 2400. This diminishing cycle,for each reflection, continues until a very high percentage of theoriginal light emitted by the LED(s) 2414 passes through the whitereflective (almost opaque) alumina and is emitted by the light source.Remarkably, extraction efficiencies of greater than 70% have beenachieved with alumina (Al2O3) elements that have less than 17% in linetransmittance. These efficiencies are measured by measuring the rawlumen output of the LED(s) 2414 themselves at a given voltage andcurrent and then measuring the output from the light recycling cavity2409 with the LED(s) 2414 (enclosed within the closed cavity) driven atthe same voltage and current. The very high number of reflections withinthe light recycling cavity 2409 and the fact that the LED's 2414 lightemitting surface faces away from the light transmitting thermallyconductive element 2400 combined with the highly reflective and whiteopaque appearance of the light transmitting thermally conductive element2400 results in a very uniform and monolithic appearance to the lightemitting surface of the light source 2401. This overcomes one of thebiggest complaints about prior art solid state light sources: that theLEDs can be seen or viewed, appearing as point sources or hot spots whenviewing the emitting surface of the light source.

Alumina is readily available in thin sheet form. However, a wide rangeof additives are used to form the material. For this application,additives which do not introduce absorption losses are preferred. Someadditive or impurities such as iron can introduce absorption in to thefinal product and therefore are not preferred. In general, materialswhich exhibit white body color are preferred. However for applicationssuch as red light sources a wider range of body colors can be used. Assuch, the most preferred light transmitting thermally conductive element2400 is one that exhibits low absorption losses over the wavelengthsemitted by the light source.

Heat generated by at least one LED 2414 and the wavelength conversionlayer 2416 is conducted through the light transmitting thermallyconductive element 2400 and transferred to the surrounding ambientwithout the need for additional heatsinking means. The thickness of thelight transmitting thermally conductive element 2400 is between 100microns and 5 mm, with 500 microns to 1 mm preferred. If there is lowlevel of scatter within the light transmitting thermally conductiveelement then the use of thicker light transmitting thermally conductiveelements 2400 is preferred. However in this particular configurationhighly scattering light transmitting thermally conductive elements 2400such as 94% to 100% alumina can be used if the absorption losses arelow. As such, sintering aids which do not color the alumina arepreferred. Also the at least one reflector 2412 should have areflectivity greater than 80% and more preferably greater than 90%. TheLED 2414 is preferably in direct thermal contact to the lighttransmitting thermally conductive element 2400. Alternatively, the LED2414 may be mounted or thermally in contact with the reflector or otherthermally conductive substrate as long as the thermal impedance betweenthe LED 2414 and the light transmitting thermally conductive element2400 is minimized. While at least one LED 2414 may be thermally attachedto at least one reflector 2412 to provide additional cooling surfacearea, it is preferred and an embodiment of this invention that themajority of the heat generated by at least one LED 2414 be transferredto the at least one light transmitting thermally conductive element2400. This allows for the light source to be mounted onto a wide rangeof surfaces which may or may not be thermally conductive such asceilings, walls, sheet rock, ceiling tiles, glass and other low thermalconductivity surfaces which may be combustible or have maximum safetemperature ranges.

In some cases it may even be advantageous to thermally isolate at leastone reflector 2412 from surfaces onto which it is mounted. This ispossible because substantially all the heat generated within the lightsource can be dissipated off the exterior light emitting surface(s) 2401of the at least one light transmitting thermally conductive element2400. Preferably, heat generated in the wavelength conversion layer 2416is also transferred to at least one light transmitting thermallyconductive element 2400 so that it may be dissipated and cooled by theexterior light emitting surface(s) 2401 of the light transmittingthermally conductive element 2400 as well. In general, this inventiondiscloses a light source with at least one light transmitting thermallyconductive element 2400 with an external light emitting surface 2401whereby the same exterior light emitting surface 2401 also transfers themajority of the heat generated in the light source to ambient. Thisincludes heat generated by the at least one LED 2414, heat associatedwith absorption losses within the light recycling cavity 2409, and anyheat generated by losses (e.g. Stoke's shift) in the at least onewavelength conversion layer 2416. At least one reflector 2412 mayadditionally be used to transfer heat from either the at least one LED2414 and/or wavelength conversion layer 2416 to at least one lighttransmitting thermally conductive element 2400. While at least onereflector 2414 could in principle also contain all or part ofinterconnect 2402 for at least one LED 2414. It should be noted howeverthat additional dielectric layers (not shown) are required to integratethe interconnect 2402 into at least one reflector 2412.

It is important that all interior surfaces of the light recycling cavityhave high reflectivity. For example reducing the reflectivity of thereflector 2412 from 95% to 90% will reduce the extraction efficiency ofthe light recycling cavity by 20%. At least one LED 2414 shouldpreferably have a high reflectivity. However, it is not that criticalbecause the LED(s) 2414 will typically cover a very small percentage ofthe inside area of the light recycling cavity. The interconnect 2402similarly also covers only a small fraction of the inside area of thelight recycling cavity 2409. However, reactivities of greater 80% areachievable and preferred for the interconnect 2402. The at least onereflector should have a reflectivity greater than 90%, and morepreferably greater than 95%. Also, the wavelength conversion layer 2416preferably should have low absorption losses. Scattering can be veryhigh in these light recycling systems as long as the loss associatedwith each reflection is minimal. With the use of mostly reflective lighttransmitting thermally conductive element 2400 a light ray 2420 may asmany as 40 reflections before exiting the light recycling cavity 2409through light transmitting thermally conductive element 2400. In aconventional light recycling cavity with a physical exit aperture thecan only exit through the exit aperture. However, using a mostlyreflective and translucent light transmitting thermally conductiveelement 2400 there is no defined physical exit aperture. Nevertheless,light does escape as described previously.

Optionally, a blocking layer 2404 may be used to prevent light from theat least one LED die 2414 and/or wavelength conversion layer 2416 frompassing through the light transmitting thermally conductive element 2400without first entering and mixing in the light recycling cavity. Thiswill assure a high degree of mixing and minimize any light “hotspots”near the LED 2414. Alternately at least one LED 2414 may be an LEDpackage where blocking layer 2404 is integrated into the LED package.

Power to at least one LED die 2414 is powered via interconnect 2402which in turn attaches to external power leads 2408 and 2406. While FIG.24 is a two dimensional view, it should be noted that interconnect 2402covers only a small amount of the surface area of interior surface 2403of light transmitting thermally conductive element 2400. External powerleads 2408 and 2406 may be but not limited to flex circuits, pins,wires, insulated wires, magnetic contacts and other physical contactingmeans. At least one reflector 2412 is preferred to be a highreflectivity coated metal such as Alanod™, but other materials bothdiffuse and specular with reflectivity greater than 90% may be used. Itcan't be seen in this cross sectional view but the reflector 2412 formsfive sides of the light recycling cavity 2409. The reflector 2412 can beeasily manufactured using conventional sheet metal processes (e.g.stamping, etc.). In general the use of inorganic materials are preferredto create non-flammable recycling cavity self cooling light sources, butreflective polymers for the reflector 2412 may be used in applicationswhere flammability is not an issue.

FIG. 25 illustrates the temperature of the LED (sometimes referred to as“die”) versus input watts to the LED (die) for two different thermalconductivities for the light transmitting thermally conductivetranslucent element 2400 previously discussed in FIG. 24. The LED diehas a maximum operating temperature Tmax as depicted by the dashed line2504. If a low thermal conductivity material such as glass with athermal conductivity of 1 W/m-K is used as the light transmittingthermally conductive translucent element 2400, the LED's maximumoperating temperature Tmax is reached at very low input power (watts)even if the thickness of the glass is made very thin. This is depictedby graph line 2500 showing the relationship between input power of theLED in watts versus LED junction temperature TJ. In this case to getusable light output, requires the use of large numbers of LED dieclosely spaced at low drive levels. When the light transmittingthermally conductive element 2400 is instead made of materials with athermal conductivity of 30 W/m-K (e.g. alumina), curve 2502 is attainedin which very high drive levels to the LED can be used while maintainingthe LED die temperature below Tmax. This enables increased spacingbetween LED die and higher drive levels for each LED die withoutexceeding the LED's maximum temperature limit Tmax. This results inhigher light output with fewer LEDs which lowers cost. In general,higher thermal conductivity materials are preferred for the lighttransmitting thermally conductive element 2400 to spread the heat outover a larger area.

FIG. 26 depicts a typical suspended ceiling 2601. Ceiling tile 2606 issuspended from the deck 2600 via anchors 2602 and wires 2604 by grid2603. Plenum space 2608 is the region above the ceiling tile 2606 andbelow the deck 2600. The office space 2609 is below the ceiling tile2606 and above the floor 2612. Occupants (or a firefighter) 2610typically occupy the office space 2609 below the ceiling 2601. A firecan propagate in either the plenum space 2608 or office space 2609. Ductwork, electrical distribution, networks and fire suppression typicallyis in plenum space 2608. In general, it is desirable to minimize thenumber and size of breaks in the suspended ceiling for acoustic,aesthetic, and fire suppression. Existing lighting fixtures such astroffers break the contiguous nature of the suspended ceiling 2601. Inmost building codes, troffers and can lights are required to be encasedin fireproof enclosures on the plenum side 2608. Unfortunately mostsolid state light fixtures depend on cooling to occur within the plenumspace 2608. The use of fireproof enclosures greatly hinders the transferof heat to the plenum space 2608. It is highly desirable, from anaesthetic, fire, and acoustical standpoint that any lighting fixture notbreak the contiguous nature of the suspended ceiling 2601 and would coolitself from or into the office space area 2609. Even more preferably anideal lighting fixture would blend aesthetically into the grid 2603and/or ceiling tile 2606 and be lightweight enough such that thelighting fixture can be seismically certified with the suspended ceilingsuch that no additional wires 2604 to support the light source arerequired. The use of high lumens/gram self cooling light sources of thisinvention provides a means of meeting these simultaneous requirements.Most preferable is that these lighting fixtures are non-flammablethereby reducing the risk to firefighters/occupants 2610 even further.In general the light sources of this invention may be installed on awall, floor, ceiling or suspended ceiling of a room such thatsubstantially all the heat generated by the light source is dissipatedinto the room or office space side 2609. The light source contains atleast two external contacts that both mechanically attach andelectrically interconnect said light source to a powered distributedgrid 2603 contained on a ceiling, wall or floor of a room wherein thelight source can be easily removed and attached to different locationson the wall, floor or grid to adjust the lighting distribution in theroom. All of this can be achieved without ever having to break orpenetrate the ceiling barrier. The light source may be integrated intomovable ceiling tiles 2606 as well.

FIG. 27 depicts a self cooling recycling solid state light source 2704attached to a 24 volt DC powered grid 2700 via magnetic contacts 2706.The conductors 2708 and 2709 are attached to grid 2700 via dielectric2710. External interconnects (not shown) connect conductors 2708 and2709 to a 24 VDC power supply (not shown) as known in the art. A typicalexample would be Armstrong's FlexZone™ DC power grid ceiling. As theself cooling light recycling solid state light source 2704 can beadapted to run on AC or other DC voltages, this embodiment is notlimited to 24 VDC power grids. The self cooling recycling solid statelight source 2704 preferably has a thickness less than 5 mm such thatthe occupant or office space side of the ceiling tile 2702 can beessentially flush with the light emitting surface 2720 of the selfcooling light recycling solid state light source 2704. This creates amonolithic look to the suspended ceiling. Even more preferable is thatthe lights off state body color of the light emitting surface 2720closely match the ceiling tile 2702 finished surface 2722 body color andtexture. The suspended grid 2700 attaches to the deck 2712 via anchor2714 and wire 2716.

FIG. 28A depicts a self cooling solid state light source recessed into aceiling tile 2802. In this embodiment, a direct attach LED die 2803 isattached to a light transmitting thermally conductive element 2808 and alight recycling cavity 2807 in fully enclosed space formed by the lighttransmitting thermally conductive element 2808 and reflector 2801. Awavelength conversion layer 2805 is applied to the direct attach LED die2803 thereby reducing the amount of wavelength conversion materialneeded and minimizing the wavelength conversion layer 2805 impact on theexternal body color. Because the ceiling tile is typically low densityand an electrically insulating dielectric which is easily penetrated,lightweight light sources can be simply pinned on or otherwise attachedwithout the need for additional support. Push pins 2810 and 2811 actlike pins in a cork board wherein they are pressed into the relativelysoft ceiling tile and are able to support and secure the very lightweight light sources of this invention. The self cooling solid statelight source can be pushed into a recessed pocket in ceiling tile 2802such that it is substantially flush with outer scrim layer 2800. Thepush pin contact not only provides an electrical connection but alsoattaches the self cooling solid state light source to the ceiling tile2802. On the plenum side of the ceiling tile 2802 clip 2804 furthersupports the self cooling solid state light source. In a manner similarto pierced earrings being held in place the clip 2804 can be used notonly to lock the source in place but also to provide electrical inputvia power leads 2806 an 2812. Because the majority of the heat istransferred by the light emitting surface 2813 to the office (occupant)space, the self cooling solid state light source can be cooled withoutbreaking the contiguous nature of the ceiling. This approach enables awide range of retrofittable light sources wherein the lightweight andlow surface temperature of the surface in contact with the mountingsurface enables the mounting of the source to combustible materials.

As a further example, push pin contacts 2810, 2811 may be robust enoughto pierce into the surface of a piece of sheetrock or dry wall. Push pincontacts 2810, 2811 may protrude part way or all the way through thesheetrock to allow for contact to electrical connection to conductorsembedded in or behind the sheetrock sheet. Flat conductors as known inthe art, which are typically used for audio applications, may also beutilized. Due to the low current nature of these sources even flatconductors mounted behind decorative wallpaper can be used to providepower to the light sources disclosed in this invention. This is possiblebecause the light sources disclosed are lightweight enough to allow forpush pin mounting and they do not require additional heatsinking means.This is all made possible because substantially all the heat generatedwithin the light source is dissipated by the light emitting surface sothat the mounting surface does not require any thermal transfer for thelight source to operate. In general, the light sources disclosed in thisinvention may be mounted to any surface via clips, magnets, or othermounting means while emitting light levels greater than 60 lumens persquare inch of emitting surface independent of the size of the lightsource. This is possible because the cooling area and light emittingarea are substantially the same. The sources may be easily secured tovirtually any surface because they also emit greater than 30 lumens pergram. Lastly, the light sources disclosed are inherently distributedsources, which do not require any additional fixturing elements.Incandescent and halogen light sources require heat shields to preventoverheating of adjacent or nearby combustible materials. Fluorescentlight sources require additional optical elements (reflectors,diffusers, etc.) to transform the tubular line of light output into alarger flat emitting source.

FIG. 28B depicts an embedded self cooling light source wherein the scrimor outside layer 2828 of the ceiling tile takes the place of thereflector to form the light recycling cavity. In this case the lighttransmitting thermally conductive element 2822 to which direct attachLED die 2824, wavelength conversion layer 2826, and push pin contacts2832 are attached simply cover the cavity or depression formed in theceiling tile 2820 and scrim layer 2828. The push pin contacts 2832 alsocan be connected and supported by clip 2818 with power supplied vialeads 2816 and 2814. In this case the scrim layer 2828 is preferablyhighly reflective at least within the region that forms the lightrecycling cavity of the self cooling solid state light source. A widerange of additional elements such as bezels and micro louvers can alsobe attached to the light emitting surface 2822 used to enhance theaesthetic and optical performance of the sources. This embodimenteliminates the need for a separate cavity reflector 2801 by takingadvantage of the high reflectivity of the scrim layer 2828. Alternately,a scrim layer 2829 can be a surface treatment on the thermallyconductive translucent element 2822. Preferably, scrim layer 2829 wouldbe thermally conductive and light transmitting in nature with minimalabsorption to the light emission from the light source. Even morepreferably, the scrim layer 2829 enhances the natural convectioncoefficient and/or radiative coefficient of the light emitting surface2823 of the light transmitting thermally conductive translucent element2822 on occupant or office side of the light source. One means makingsuch a scrim layer 2829, is the use of flame spraying alumina powdersand/or fibers applied directly to an alumina light transmittingthermally conductive translucent element (e.g. alumina) 2822. Becausethe light recycling cavity allows for a wide range of translucency inthe light transmitting thermally conductive translucent element,materials with in-line transmission less than 20% can be used and stillmaintain efficiency levels greater than 70%.

Alternatively, highly reflective totally opaque materials that havearrays of holes or openings representing a substantial percentage of thesurface area can be used for the light transmitting thermally conductiveelement 2822. As an example, a metal core board containing an array ofsmall holes through the metal core board may be used as the lighttransmitting thermally conductive element 2822. As long as the surfacesthat make up the recycling cavity are highly reflective to allow forlong optical pathlengths, large number of light bounces, or a lot ofrecycling either homogenous or in-homogenous materials may be used forthe light transmitting thermally conductive translucent element 2822. Itshould be noted that a holey metal core board preferably also has highreflectivity within the holes through the metal core board. The holes inthe holey metal core board most preferably are greater than 10% of thesurface area of the holey metal core board. The hole may be uniformlydistributed or non-uniformly distributed. Smaller holes are preferablewith a range of 1 micron to several millimeters in diameter. The higherthermal conductivity of the metal core allows for the thermallyconductive translucent element 2822 to thinner using this approach.Additional dielectric, diffusive elements, or imaging elements may beused to construct composite thermally conductive translucent element2822. As an example, highly reflective porous aluminum 100 microns thickwith 20 micron diameter holes uniformly distributed across the aluminumis laminated with a 40 micron thick flexible zirconia sheet as know inthe industry. A silver thick film interconnect is printed and fired onthe 40 micron thick flexible zirconia prior to lamination. The resultingcomposite may be used as thermally conductive translucent element 2822.

Optionally an additional scrim layer 2822 may be attached to the othersurface of the aluminum to provide aesthetic, acoustical, or thermalbenefits. In general, the side of the holey metal core board, which innot part of the recycling cavity may be painted, printed, or otherwisedecorated to create a wide range of aesthetic looks. This approach is anexample of a non-homogeneous thermally conductive translucent element2822. Also, the holey metal core board as thermally conductivetranslucent element 2822 can be used to allow for enhanced heat transferto the office space side of the installation or even to allow for airflow through the light source. In the later case, the reflector also hasa pathway for airflow. Most preferably this approach is used in porousmetal ceiling tile applications. As an example a porous metal ceilingtile is patterned with a highly reflective dielectric layer and a highlyreflective interconnect to form thermally conductive translucent element2822. An optional scrim layer 2828 can be added for aesthetic, thermal,or acoustic reasons. LED direct attach die 2824 with a wavelengthconversion layer 2826 or LED packages with wavelength conversion alreadyincluded can be attached to the highly reflective interconnect on thehighly reflective dielectric which is on the porous metal ceiling tilewhich forms the thermally conductive translucent element 2822.

Reflector 2801 may or may not contain a pathway for air flow dependingon the installation and desired optical output. In this example, thelight source can be the ceiling tile not attached to the ceiling tile.Further, the scrim layer 2828 may be a light transmitting thermallyconductive layer such that the light source blends into the ceilingaesthetically but still allows for light emission and thermal cooling ofthe light sources.

FIG. 28C depicts a holey light transmitting thermally conductive element2861 comprising of at least three layers a metal core 2860, dielectricreflector layer 2856, and interconnect 2854. An optional fourth layer2858 may be added as described below. Metal core 2860 typically is madeout of a metal including but not limited to aluminum, copper, metalalloys, and metal composites. Metal core most preferably has the thermalconductivity greater than 30 W/m-K and even more preferably greater than100 W/m-K. Dielectric reflector layer 2856 most preferably has areflectivity greater than 90% and even more preferably greater than 95%.The dielectric reflector 2856 may cover all or only a portion of insidesurface 2872. Dielectric reflector layer 2856 electrically isolatesinterconnect 2854 from the metal core 2860 allowing for power to bedelivered to LED die 2852. LED die 2852 may further be coated withwavelength conversion layer 2850.

In general, a light recycling cavity reflector element 2870 reflects2881 and redirects at least a portion of the light emitted 2880 from theLED die 2852 and wavelength conversion layer 2850 onto the insidesurface 2872 of the holey light transmitting thermally conductiveelement. Some of those light rays are reflected 2882 off of surface2872. Those light rays which are not reflected off inside surface 2872of dielectric reflector layer 2856, either transmit light rays 2866through the hole 2862 or the light rays 2864 may bounce of the sidewallsof hole 2862 before exiting. Holes 2862 may be perpendicular to theinside surface 2872 or tilted such that the ratio of light rays 2864 tolight rays 2866 increases. It is important that the inside sidewall 2876of hole 2862 is highly reflective to achieve high light extractionefficiency from the light recycling cavity formed by the holey lighttransmitting thermally conductive element 2861 and the reflector 2870.Alternately, inside sidewall 2876 may be absorptive if it is desirableto restrict the angular output distribution of the light source. Theinside sidewall 2876 may also be tapered forming reflective opticalelements which again can be used to modify the output light distributionfrom the light source. For example, if the opening of the holes 2885 issmaller than the light output end of the holes 2886 the light raysreflected off the inside of the holes will be collimated. Because thelight transmitting thermally conductive element disclosed is nothomogenous, an optional outside layer 2858 may be added which can have awide range of colors and/or finishes without negatively affecting thelight recycling cavity efficiency. Most preferably outside layer 2858 isthermally conductive and exhibits a high thermal emissivity aspreviously described. Most preferred is an outside surface 2874 whichhas an emissivity greater than 0.3.

FIG. 29 depicts a suspended self cooling light fixture 2916 within asuspended ceiling. Cables 2914 and 2918 attach to the grid 2920 and 2910respectively, which contain power leads 2912 and 2913 respectively.Cables 2914 and 2918 provide both physical support and electrical inputto the suspended self cooling light recycling light source fixture 2916.Alternately, the power leads 2912 and 2913 can come through the ceilingtile 2908 with cables 2914 and 2918. Because lumen per gram outputs aregreater than 50 lumens per gram a 2000 lumen suspended self coolinglight source fixture 2916 weighs less than 40 grams which is well withinthe safe structural capacity for either the grid or the ceiling tiles tosupport. This increases the flexibility for the lighting designer.Unlike conventional large, heavy and fixed light fixtures such astroffers, virtually no falling or seismic hazard exists with thisapproach to lighting. With prior art heavy light source fixtures thereis a significant risk especially for firefighters/occupants 2924 duringa fire where lighting fixtures can fall out of the suspended ceiling.Aesthetically the suspended ceiling supported by wires 2904, anchors2902 to deck 2900 hides air ducts, wiring, and fire suppression means inthe plenum space 2906. The firefighters/occupants 2924 view is theoffice space defined by suspended ceiling, floor 2922, and walls. Thelight source(s) 2916 of this invention use the combination of lightweight and light output to enable sufficient light in a space such thatthe total weight of the light source divided by the square footage ofthe illuminated area or space is less than 1 gram per square foot whileproviding over 30 foot candles to the illuminated area.

FIG. 30 depicts the use of self cooling solid state light recyclingcavity light sources 3012 and 3014 within a seismic suspended ceilinginstallation. During a seismic event the deck 3000, floor 3006 and walls3002 and 3004 move relative to each other which stress the suspendedceiling 3001 comprising of the grid 3034, the ceiling tile 3010supported by wires 3032 anchored via anchors 3030 attached to the deckattachment 3008. The suspended ceiling 3001 may also be attached to thewalls 3004 and 3002 with supports 3020 and 3022 respectively. Gridsupported self cooling solid state light source 3012 is attached to grid3034 while embedded self cooling solid state light sources 3014 isattached to or embedded within the ceiling tile 3010. In either case theself cooling solid state light sources do not interfere with thedampening and supporting function of the either the grid 3034 or theceiling tile 3010 because they have such low thermal mass and becausethey do not form a break in the suspended ceiling. The flexibility ofthis approach permits a wide variety of suspended ceiling installationswithout compromising the structural integrity or the contiguous barrierof the suspended ceiling. The lighting may be easily configured orchanged without compromising the safety of the occupants in the event ofa seismic event.

FIG. 31A depicts a suspended ceiling system 3101 supported by wires 3103and 3104 anchored via anchors 3102 to the deck 3100 containing the selfcooling solid state light source 3112 of this invention embedded withina ceiling tile 3020 and containing the self cooling solid state lightsources 3110 of this invention on the grid 3106. Using this approach,the acoustical response of the suspended ceiling is not compromised bythe lighting fixtures. In conventional installations, large breaks inthe noise dampening occurs because ceiling tiles 3108 are replaced bytroffers with little to no acoustical treatment (e.g. dampening) orcapability. This increases the noise level for the occupants 3114 assound waves bounce between the floor 3116 and the suspended ceiling. Byvirtually eliminating all breaks in the suspended ceiling 3101 the noiselevel within the office space can be reduced because the acousticallyfunctional ceiling tiles (e.g. 3108, 3120 and 3121) form a contiguousbarrier between the plenum space 3105 and the occupant side 3107 of thesuspended ceiling 3101. Also noise transmitted from the plenum space3105 (established by and between the suspended ceiling 3101 and the deck3100) is reduced to the occupant or office space 3107 and the occupants3114 with the more contiguous suspended ceiling enabled by the lightsources of this invention. In general, the more contiguous the suspendedceiling the less acoustical noise and the lower the fire risk for theoccupants 3114.

Referring now to FIGS. 31A-C concurrently, the suspended ceiling system3101 generally comprises a support grid 3106 formed by a plurality ofintersecting struts 13100. The support grid 3106 is supported within aninternal space of a building. The intersecting struts 13100 form aplurality of grid openings 13101. A plurality of ceiling tiles 3108,3120 and 3121 are mounted to the support grid 3106 and positioned in thegrid openings 13101 to collectively form a barrier. Each of the ceilingtiles 3108, 3120 and 3121 comprises a front surface 13102 and a rearsurface 13103 opposite the front surface 13102. The front surfaces 13102of the ceiling tiles 3108, 3120 and 3121 facing an occupant portion 3107of the internal space of the building. The front surfaces 13102 of theceiling tiles 3108, 3120 and 3121 define a reference plane A-A. Theoccupant portion 3107 of the internal space is located below thereference plane A-A.

The suspended ceiling system 3102 further comprises a plurality of solidstate light sources 3112, 3110. The solid state light sources 3110 aremounted to the struts 13100 of the support grid 3106. The solid statelight source 3112, however, is integrated into the ceiling tile 3120,thereby collectively forming an integrated ceiling panel and lightingapparatus 13500. The solid state light sources 3112, 3110 can take theform of any of the solid state light sources discussed herein. Forexample, and as discussed in greater detail in this application, thesolid state light sources 3112, 3110 generally comprise a reflectorelement 3200, a light emitting diode (LED), such as LED die 3204, and alight transmitting thermally conductive element 3202. The lighttransmitting thermally conductive element 3202 provides a common lightemitting and cooling surface 3205 to dissipate a majority of the heatfrom the solid state light source 3112. The common light emitting andcooling surface 3205 faces the occupant portion 3107 of the internalspace. As can be seen, the solid state light source 3112 is at leastpartially embedded in and supported by the ceiling tile 3120.

The reflector element 3200 and the light transmitting thermallyconductive element 3202 collectively form a light recycling cavity 3203.The LED 3204 is mounted on the light transmitting thermally conductiveelement 3202 in the light recycling cavity 3203. Light emitted by theLED 3204 is redirected within the light recycling cavity 3203 by thereflector element 3200 and passes through and exits from the solid statelight source 3112 via the light transmitting thermally conductiveelement 3202 through the common light emitting and cooling surface 3205.The common light emitting and cooling surface 3205 of the lighttransmitting thermally conductive element 3202 acts as the primary heatdissipation means of the LED, and the light source 3112.

Each of the ceiling tiles 3108, 3120 and 3121 comprises a side edge13104 extending between the front and rear surfaces 13012, 13103 andhaving a profile that engages the struts 13100 to support the entireweight of the ceiling tile 13012, 13103. Moreover, the entire weight ofthe solid state light source 3112 is supported by the ceiling tile 3120.Thus, the entire weight of the integrated ceiling panel and lightingapparatus 13500 is supported in the support grid 3106 by the cooperationof the side edge 13104 of the ceiling panel 3120 and the flange portionof the struts 13100. The total weight of the solid state light source3120 and all heat sinking for the solid state light source 3120 is lessthan one gram per square foot yet provides greater than 30 lumens persquare foot of illumination throughout an illuminated area of theoccupant portion 3107 of the internal space.

The ceiling tile 3120 comprises a recess 13105 formed into the frontsurface 13102 of the ceiling tile 3120. The recess 13105 is defined by arecess sidewall 13106 and a recess floor surface 13107. The recesssidewall 13107 extends from the front surface 13102 of the ceiling tile3120 to the recess floor surface 13106. The solid state light source3112 is disposed in the recess 13105 and mounted to the ceiling tile3120. In the exemplified embodiment, the recess sidewall 13107circumferentially surrounds a side edge 13108 of the solid state lightsource 3112 when mounted within the recess 13105. In one specificembodiment, the side edge 13108 of the solid state light source 3112 isin surface contact with the recess sidewall 13107 when the solid statelight source 3112 is mounted within the recess 13105. The solid statelight source 3112 also comprises a rear surface 13109 opposite thecommon light emitting and cooling surface 3205. The rear surface 13109of the solid state light source 3112, in certain embodiments, is insurface contact with the recess floor surface 13106 when the solid statelight source 3112 is mounted within the recess 13105. In the exemplifiedembodiment, the solid state light source 3112 is embedded in the ceilingtile 3120 so that the common light emitting and cooling surface 320 ofthe light transmitting thermally conductive element 3202 issubstantially flush with the front surface 13102 of the ceiling tile3120.

The ceiling tile 3120 has a thickness t1 measured from the front surface13102 to the rear surface 1303. The recess 13105 has a depth dl measuredfrom the front surface 13102 to the recess floor surface 13106. In oneembodiment, the thickness t1 is greater than the depth dl.

In certain embodiment, each of ceiling tiles 3108, 3120 and 3121 maycomprise a core 13110 and a scrim 13111 (see FIG. 31C). The scrim 1311may comprise the front surface 13102 of the ceiling tiles 3108, 3120 and3121. In certain arrangement, the recess floor surface 13106 may beformed by a portion of the core 13110.

The core 13110 may be formed of a fibrous mat, such as those formed fromsynthetic fibers, such as mineral wool, fiberglass, polymer fibers(e.g., nylon fibers) or metal fibers. Alternatively, the core can beproduced from recycled textile fiber such as cotton, linen, and wool.Vegetable fibers such as flax, hemp, kenaf, straw, waste paper, and woodfiber can also be used to produce the core. Fillers such as kaolin clay,calcium carbonate, talc, mica, Wollastonite, or inorganic flameretardant fillers are also used within the core 13110. The core 13110may also be treated with fire retardant materials as is well understoodin the art of making ceiling tiles. The scrim 13111 may be formed asdiscussed herein and is known in the art. For example, the scrim 13111may be a light transmitting thermally conductive scrim. In certain otherembodiments, discussed elsewhere herein, the light transmittingthermally conductive scrim may utilized so as to overlay the commonlight emitting and cooling surface 3205 of the light transmittingthermally conductive element 3202 to optically conceal the solid statelight source 3112. Such a light transmitting thermally conductive scrimmay comprise alumina fibers.

In certain other arrangements (also discussed elsewhere herein), a lighttransmitting thermally conductive scrim may be applied to the commonlight emitting and cooling surface 3205 of the light transmittingthermally conductive element 3202. In one such arrangement, the lighttransmitting thermally conductive scrim may have a color and texturethat matches the front surface 13102 of the ceiling tile 3120. The lightsource 3112 may also comprise push pin contacts 3618, 3616 (alsodiscussed herein elsewhere) that electrically couple to the LED andpenetrate the ceiling tile 3120 to mounting the light source 3112 to theceiling tile 3120.

FIG. 32A depicts a light recycling self cooling light source 3201comprising a light transmitting thermally conductive translucent element3202 to which a direct attach LED die 3204 is attached. (It should benoted that in most of the figures of the individual light sources hereinthe light emitting surface of the light source is depicted or shownfacing in an upward direction. Of course, in ceiling installations thelight emitting surfaces would be facing downward.) The direct attach leddie 3204 further is coated with a wavelength conversion layer 3206. Thelight recycling cavity 3203 is formed by the reflector element 3200forming an enclosure or cavity around the light transmitting thermallyconductive element 3202. As previously described, light rays generatedand emitted by LED 3204 within the light recycling cavity are reflectedand recycled by reflector 3200 to the light transmitting thermallyconductive translucent element 3202 where they are reflected back intothe cavity 3203 or transmitted through to the light emitting surface3205 of the light transmitting thermally conductive element 3202.Multiple reflections provide high uniformity to the light emittingsurface 3205. Uniformity can be further enhanced with the addition of aturning element 3208 on reflector 3200 which redirects light raysemitted normal to the emitting face of the LED 3204 down the length ofthe recycling cavity. In particular a conical, pyramidal, or cusp shapedturning element 3208 can be used to increase the optical pathlength oflight rays within the light recycling cavity which in turn increasesspatial uniformity for the light rays exiting the thermally conductivetranslucent element 3202. The turning element 3208 may be a separatepiece, sheet, or formed directly into the reflector 3200. A metal orreflective inorganic is preferred for reflector 3200. However, becausethe majority of the heat is transferred to the ambient via the surfaceof the light transmitting thermally conductive translucent element 3202the reflector 3200 does not need to be thermally conductive andtherefore can be formed in virtually any material including multilayeredreflectors like 3M's ESR films, metal coated films, diffuse reflectivefilms such as polysilazane containing Hex-Boron-Nitride (hBN) flakes,and other inorganic and/or organic reflectors. Most preferred arereflectors with greater than 90% reflectivity. Non-flammable materialssuch as metals and ceramics are preferred.

FIG. 32B depicts another embodiment of the light source of the presentinvention containing a light transmitting thermally conductive element3220 combined with reflector 3224, which forms light recycling cavity3227. Direct attach LED die 3228 emits blue light which is partiallyconverted to longer wavelengths by wavelength conversion layer 3229. Thewavelength conversion layer 3229 location is optional within the lightrecycling cavity 3227. Alternatively there may be no wavelengthconversion layer. For example red, green and/or blue LEDs may be usedsingly or together within the light recycling cavity 3227. A tunablelight source is easily achieved with a high degree of mixing of thevarious colors within the light recycling cavity. Single color selfcooling light sources and multicolored self cooling light sources mayalso be constructed using this approach. The use of direct attach LEDs3228 is preferred. However, because the interconnect (not shown in thisview but previously described), which is typically on the inside surface3225 of the light transmitting thermally conductive element 3220, willaccommodate direct attach, flip chip, wirebond or other connectionmethods a variety of LED die and LED packages can be used. In thisembodiment scattering elements 3226 are used to adjust the spatialuniformity of the light rays exiting the thermally conductivetranslucent element 3220.

FIG. 32C depicts a light recycling cavity in which the reflector 3332 isformed to redirect light out through the light transmitting thermallyconductive element 3330. The direct attach LED die 3336 and wavelengthconversion layer 3338 emit light into the light recycling cavity 3335formed by reflector 3332 and light transmitting thermally conductiveelement 3330. Additional scattering or turning elements 3334 and 3340can be used to spatially redirect light within the recycling cavity outthrough the light transmitting thermally conductive element 3330. Theturning element 3334 also depicts the ability to tune the uniformityafter assembly of the recycling cavity by inserting turning elements3334 through holes in the reflector 3332. The turning elements can beadjusted to present different reflective faces to the light emanatingfrom the LED 3336 to alter the light distribution in the recyclingcavity 3335. Alternately, opaque or translucent reflective elements canbe spatially printed on the light transmitting thermally conductiveelement 3330 and used with or without turning element 3340 to controlthe number of reflections before the light rays escape the recyclingcavity 3335. As an example, highly reflective small dots may be printedat the same time the silver thick film interconnect is printed on thelight transmitting thermally conductive element 3330. These dots can bepatterned with varying spatial density to alter the distribution oflight emanating from the light recycling cavity.

FIG. 32D depicts a light recycling self cooling light source with anadditional waveguiding element 3352 that more or less fills the lightrecycling cavity. In this embodiment the direct attach LED die 3356 andwavelength conversion element 3358 transfer their heat to the thermallyconductive translucent element 3346. However light emanating from theLED and wavelength conversion element 3359 is coupled to the waveguide3352. Light extraction from the waveguide 3352 occurs due to lightextraction elements 3354, 3355 and 3357. Extraction element(s) 3357 maybe as simple as an index matching dot between waveguide 3352 and lighttransmitting thermally conductive element 3346. The reflector 3350 isstill used to enhance the recycling within the light source and it maybe separate from or be formed on the waveguide 3352 as a highreflectivity coated film.

FIG. 33 depicts a graph illustrating the importance of reflectivity onthe efficiency of light recycling cavities. Due to the large number ofreflections that must occur to convert a point source like an LED die toa uniform and diffuse output, any losses in the light recycling cavitycaused by the LED die, interconnect, reflector, and/or within thethermally conductive translucent element need to be minimized. It ispreferable that all of these components have high reflectivity(e.g. >80%). However, the LEDs are not as critical as they represent avery small portion of the inside surface of the recycling light cavity.The reflector 3200 as shown in FIG. 32A will typically represent over60% of the inside surface area of the light recycling cavity 3203.Therefore, it is preferred that the reflector 3200 has very highreflectivity (e.g. greater than 95%) The light transmitting thermallyconductive elements disclosed herein are most preferably optically lowabsorption loss materials such as alumina, sapphire, YAG, glass, YSZ,GGG, and other optically low absorption materials. It should be notedthat in line transmission number typically used are not a good indicatorof optical losses. Because recycling cavity sources such as these allowfor multiple bounces, highly scatter materials such as alumina whichappear white or opaque can actually be very efficient windows. Thecritical issue is not in-line transmission but optical absorptionlosses. Alumina Al2O3 has very low optical absorption throughout thevisible spectrum however if improper sintering aids are used absorptionlosses can be increased. Therefore, high purity materials are preferredwhich may or may not be amorphous, polycrystalline or single crystal innature. The same is true for organic materials, Teflon films with highporosity have some of the highest diffuse reflectivity numbers that canbe generated approaching 100%. This effect is due to the low opticalabsorption throughout the visible region for these materials. Compositescan likewise be low absorption as is the case with polysilazane and hBNcomposites, which have been previously disclosed, in the referencedfilings by the authors. In general, material with absorption losses lessthan 0.1 cm-1 in their transparent state throughout the visible regionare preferred for the thermally conductive translucent element.

The use of organic materials to further enhance the reflectivity insidethe recycling light cavity or to add aesthetic features to the outsideof the light source is also disclosed. Examples of low opticalabsorption materials include spin-on glasses, polymers, monomers,oligomers, waxes, and oils. Other optically useful materials includecomposites and mixtures including inorganic/organic suspensions,polymers containing organometallics, and sol-gels. These low opticalabsorption materials can be formed, cured, crosslinked, or otherwisedensified using heat, actinic radiation, pressure, shear, electron beam,mechanical or chemical means to form a layer or freestanding element.

Preferred optical materials include the following: Typical spin-on glassmaterials include methylsiloxane, methylsilsesquioxane, phenylsiloxane,phenylsilsesquioxane, methylphenylsiloxane, methylphenylsilsesquioxane,and silicate polymers. Spin-on glass materials also includehydrogensiloxane polymers of the general formula (H0-1 0SiO1.5-2.0)x andhydrogensilsesquioxane polymers, which have the formula (HsiO1.5)x,where x is greater than about 8. Also included are copolymers ofhydrogensilsesquioxane and alkoxyhydridosiloxane orhydroxyhydridosiloxane. Spin-on glass materials additionally includeorganohydridosiloxane polymers of the general formula(H0-1.0SiO1.5-2.0)n(R0-1.0SiO1.5-2.0)m, and organohydridosilsesquioxanepolymers of the general formula (HSiO1.5)n(RSiO1.5)m, where m is greaterthan 0 and the sum of n and m is greater than about 8 and R is alkyl oraryl.

Typical polymer optical materials include halogenated polyalkylenes,preferred fluorinated an/or chlorinated polyalkylens, more preferredchlorofluoropolyalkylens, and most preferred are the fluorinatedpolyalkylenes among which are included: polytetrafluoroethane(ethylene), polytrifluoroethylene, polyvinylidene fluoride,polyvinylfluoride, copolymers of fluorinated ethylene or fluorinatedvinyl groups with non-fluorinated ethylenesor vinyl groups, andcopolymers of fluorinated ethylenes and vinyls with straight orsubstituted cyclic fluoroethers containing one or more oxygens in thering. Also included in the most preferred polymers are poly(fluorinatedethers) in which each linear monomer may contain from one to four carbonatoms between the ether oxygens and these carbons may be perfluorinated,monofluorinated, or not fluorinated.

Also included in the most preferred polymer optical materials arecopolymers of wholly fluorinated alkylenes with fluorinated ethers,partly fluorinated alkylenes with wholly fluorinated ethers, whollyfluorinated alkylenes with partly fluorinated ethers, partly fluorinatedalkylenes with partly fluorinated ethers, non-fluorinated alkylenes withwholly or partly fluorinated ethers, and non-fluorinated ethers withpartly or wholly fluorinated alkylenes.

Also included among the most preferred polymer optical materials arecopolymers of alkylenes and ethers in which one kind of the monomers iswholly or partly substituted with chlorine and the other monomer issubstituted with fluorine atoms. In all the above, the chain terminalgroups may be similar to those in the chain itself, or different.

Also among the most preferred polymer optical materials are substitutedpolyacrylates, polymethacrylates, polyitaconates, polymaleates, andpolyfumarates, and their copolymers, in which their substituted sidechains are linear with 2 to 24 carbon atoms, and their carbon atoms arefully fluorinated except for the first one or two carbons near thecarboxyl oxygen atom such as Fluoroacrylate, Fluoromethacrylate andFluoroitaconate.

Among the more preferred polymer optical materials, one includesfluoro-substituted polystyrenes, in which the ring may be substituted byone or more fluorine atoms, or alternatively, the polystyrene backboneis substituted by up to 3 fluorine atoms per monomer. The ringsubstitution may be on ring carbons No. 4, 3, 2, 5, or 6, preferably oncarbons No. 4 or 3. There may be up to 5 fluorine atoms substitutingeach ring.

Among the more preferred polymer optical materials, one includesaromatic polycarbonates, poly(ester-carbonates), polyamids andpoly(esteramides), and their copolymers in which the aromatic groups aresubstituted directly by up to four fluorine atoms per ring one by one onmore mono or trifluoromethyl groups.

Among the more preferred polymer optical materials, arefluoro-substituted poly(amic acids) and their corresponding polyimides,which are obtained by dehydration and ring closure of the precursorpoly(amic acids). The fluorine substitution is effected directly on thearomatic ring. Fluoro-substituted copolymers containingfluoro-substituted imide residues together with amide and/or esterresidues are included.

Also among the more preferred polymer optical materials are parylenes,fluorinated and non-fluorinated poly(arylene ethers), for example thepoly(arylene ether) available under the trade name FLARE™ fromAlliedSignal Inc., and the polymeric material obtained fromphenyl-ethynylated aromatic monomers and oligomers provided by DowChemical Company under the trade name SiLK™, among other materials.

In all the above, the copolymers may be random or block or mixturesthereof.

In general, low optical absorption plastics are preferred (fluorinatedpolymers, polysiloxanes, polysilazanes, halogenated polymers,non-halogenated polymers, polycarbonates, acrylics, silicones, andinorganic/organic composites comprising low optical absorptionorganics). An example of a low absorption strongly scattering polymericfilm is WhiteOptic™ While this film exhibits low absorption losses andwhite body color it also has very low thermal conductivity. While thismaterial can be used for parts of the recycling cavity, which are notused to cool the LED, materials with thermal conductivity higher than 1W/mK are preferred for the light transmitting thermally conductiveelements disclosed in this invention. In general, all unfilled organicmaterials exhibit low thermal conductivity (less than 1 W/mK andtypically less than 0.1 W/mK) cannot be used effectively to spread theheat generated in the LEDs within the light recycling cavity. While onecould in theory operate the LEDs at such a low level and use hundreds ofLEDS within the recycling cavity and use a lower thermal conductivitymaterial for the light transmitting thermally conductive element thecost would be excessive. In almost all solid state light sources theLEDs typically represent 50% to 80% of the overall cost.

The light source of this invention enables the minimum number of LEDswhile eliminating the need for costly appended heatsinks. Based onexperimental results greater than 5 W/mK is preferred and greater than20 W/mK is most preferred. In addition, most unfilled polymer systems,which exhibit low optical absorption have low use temperatures typicallybelow 150° C. and even below 1000 C. Therefore, strongly scatteringorganic materials which can withstand greater than 2000 C are preferredand even more preferred are organic materials which can withstandgreater than 3000 C. High quality low resistance interconnectscompatible with wirebonding and/or direct die attach fire attemperatures over 4000 C. Also direct die attach LEDs typically solderat greater than 3000 C. While lower temperature interconnects andconductive adhesive may be used there are significant tradeoff isperformance both electrically and optically. Finally, most unfilledorganic materials also are flammable. As such inorganic materials likealumina or porous metal foils are preferred. However organic/inorganiccomposites are possible.

As an example of thermally conductive inorganic/organic composite with athermal conductivity over 5 W/mK capable of withstand greater than 3000C, is boron nitride filled polysilazane may be used to form either athermally conductive layer on the porous flexible metal foils orinorganic light transmitting thermally conductive elements or be used asa freestanding element forming at least one face of the recycling lightcavity. Other polymeric binders are also possible however the hightemperature performance, optical transparency and compatibility of thepolysilazanes with boron nitride make this inorganic/organic composite apreferred materials choice. Filled thermoplastic composites areespecially preferred.

FIG. 34 depicts decorative overlay 3404 printed or otherwise formed onlight transmitting thermally conductive element 3402. In this manner thevisible light emitting surface 3410 of the light transmitting thermallyconductive element 3402 can be modified aesthetically. The lightrecycling cavity self cooling light source is again formed using areflector 3400 and a light transmitting thermally conductive element3402. Decorative overlay 3404 may include paints, lacquers, fused glass,or other coatings that impart patterns, textures and other aestheticelements. Because inorganic materials such as alumina is preferred forlight transmitting thermally conductive element 3402 high temperatureprocessing steps such as glazing are possible. These high temperaturesteps tend to also use materials like glass and other inorganics, whichstill have reasonable thermal conductivity. Texture may be imparted viaa coating on or direct embossing of the light transmitting thermallyconductive element 3402. The decorative element 3404 most preferably isthermally conductive such that when the thermally conductive decorativeelement 3404 is in thermal contact with the light transmitting thermallyconductive element 3402 the majority of the heat is emitted from theexterior surface of the thermally conductive decorative element 3404.Like a lamp shade the decorative element 3404 may or may not betransmissive to all wavelengths emitted by the light source. Coloredglasses in a variety of patterns fused to the light transmittingthermally conductive element 3402 is a preferred embodiment ofdecorative element 3404.

FIG. 35A depicts a light recycling self cooling light source withreflector 3500 and thermally conductive translucent element 3502 towhich an LED die 3508 is attached. Wavelength conversion elements 3504and 3506 maybe placed not in direct contact with LED 3508 as shown.Light emitted by the LED 3508 is reflected and recycled in lightrecycling cavity 3507 formed by reflector 3500 and light transmittingthermally conductive element 3502. A portion of the light is convertedto longer wavelengths by the wavelength conversion elements 3504 and3506 before being transmitted to and emitted by the emitting surface3503 of the light transmitting thermally conductive element 3502. Inthis configuration a UV LED die 3508 is preferred so that the phosphorsused in wavelength conversion elements 3504 and 3506 can have naturalwhite body color. Alternately, the external body color of the lightsource can be modified by selecting phosphors, quantum dots, and otherwavelength conversion materials with a particular body color. Body coloris an important aesthetic attribute of light sources when the desire isto create a monolithic uniform look in installations like suspendedceilings.

FIG. 35B depicts a light recycling self cooling light source where thelight transmitting thermally conductive element 3512 is alsoluminescent. As mentioned previously a wide range of materials can beused to form solid wavelength conversion elements in ceramic, coated,and single crystal form. The LED die 3514 attaches and is in thermalcontact to the light transmitting thermally conductive element 3512 andthe light recycling occurs due the reflector 3510.

FIG. 35C depicts a separate wavelength conversion coating/element 3524formed on or attached to thermally conductive translucent element 3522.The relative position of these two elements to the LED die 3526 may beswitched or used as shown. Reflector 3520 and light transmittingthermally conductive element 3522 form the recycling cavity.

FIG. 35D depicts a self cooling light source without a light recyclingcavity. In this embodiment the emission from the LED die 3532 which isattached to, interconnected (not shown) and cooled by thermallyconductive translucent element 3530 only partially illuminateswavelength conversion layer 3534. A wide range of optical effects can beformed using this approach, which illustrates the flexibility ofeliminating the heatsink by integrating the cooling and emissionsurfaces into one element.

FIG. 36 depicts a push pin connector for ceiling tiles 3608. Selfcooling solid state light source 3614 contains two substantially rigidpins 3618 and 3616. Because the ceiling tile 3608 is a dielectric andtends to be easily pierced the rigid pins 3618 and 3616 can be simplypressed through the scrim layer 3610 and ceiling tile 3608. Additionalmounting support can be via clips 3604 and 3606 which can additionallyact as electrical connector to power leads 3602 and 3600. The ultralight weight of these light sources resulting in high lumens per gram ofthese self cooling solid state light source 3614 allows for this type ofinstallation. Aesthetic elements 3612 can be added as well. The use ofnon-flammable materials is preferred for aesthetic elements 3612.Alternately, the scrim layer 3610 can be formed to create recesses forthe self cooling solid state light source 3614. Optionally magneticconnectors 3632 and 3630 may be used to allow for front side removalwithout removing the ceiling tile 3608. Optionally magnetic push pinswith their visible mating contacts coated to blend with the ceiling tilemay be used. In this way Self cooling light sources with greater than 30lumens per gram are preferred and embodiments of this invention.

FIG. 37 depicts a self cooling solid state light source embedded withina ceiling tile 3700 underneath the scrim layer 3708. In thisconfiguration a translucent scrim with a reasonable porosity or thermalconductivity is preferred such that heat from the thermally conductivetranslucent element can be extracted to the ambient of the office space.The heat from the LED die 3706 and reflector 3702 are again used tocreate a light recycling cavity as previously disclosed. In thisconfiguration the electrical interconnects 3710 and 3712 can be embeddedunder the scrim layer 3708 as well. This creates an illuminated ceilingtile that replaces conventional light fixture.

FIG. 38 depicts a modular rail self cooling light source, which is fieldreplaceable. In order to be field replaceable several criteria must bemet, including but not limited to easy installation, keyed installationor electrically/mechanically protected installation, low voltageoperation, distributed power, light weight, and decorative elements tocover unused areas. Armstrong FlexDC™ suspended ceiling grid offers oneexample of a distributed power system. However, prior to this inventionthe lack of field replaceable light sources due to weight and thermalconsiderations restricted taking advantage of the full capability ofthese new distributed power grids. In this embodiment a light recyclingcavity light source is integrated into a modular grid system 3800. Inthis case the reflector 3814 in previous examples is integrated into thegrid along with DC input strips 3804 and 3802 to form a light recyclingcavity modular grid system 3800 such that only the light transmittingthermally conductive element 3806 with attached LEDs and/or LED packages3812, an interconnect (not shown), and an attachment/contact means 3810and 3806 are required by the end user to create self cooling linearlight sources. This is enabled by the basic nature of this designwherein substantially most of the heat from the light source istransferred to the occupant 3816 side or office space 3818 from thelight emitting surface 3813 of the light transmitting thermallyconductive element 3806. The office space 3818 is that area below theceiling 3814 in which the occupants 3816 work. In this configuration,the light recycling cavity is formed once the translucent thermallyconductive element 3806 with its associated LEDs and/or LED packages3812 and contacts 3808 and 3810 are mounted into the reflectivereceptacle 3819 of the modular grid system 3800. While magnetic contactsare preferred for contacts 3810 and 3808, other methods are may be usedincluding but not limited to conductive Velcro™, snaps, push pins,clips, and other mechanical/adhesive means. The lightweight and longlife nature of this approach eliminates the need for expensive lockingmeans to support the field replaceable light source.

The use of standard steel grid, which allows for magnetic contacts 3808and 3810 to make contact to DC strips 3804 and 3802 is preferred. Thisapproach minimizes the weight of the light source itself, which in turnreduces the cost of shipping and storage. A distributed power grid withan integrated reflector 3819 is an embodiment of this invention. Theceiling 3814 may be a suspended ceiling, cloud, or otheraesthetic/acoustical element. While ceilings are shown, similarinstallations in walls and floors may also be utilized for thisinvention. Walls, sheetrock, brick, mortar, wood and other elements maybe used in a similar manner as a receptacle for the self cooling lightsource. The ability to transfer the heat into the office space usingsubstantially only the light emitting surface enables the use oftemperature sensitive materials including but not limited to wallpaperand paint on any mounting surface as well. In general, the light sourcesdisclosed herein may be installed on a wall, floor, ceiling or suspendedceiling of a room such that substantially all the heat generated by thelight source is dissipated into the room. The room being defined as theilluminated area or space in to which the light emitted by the lightsources is emitted.

FIG. 39 depicts a magnetic connector with self centering for modularrail or grid system. In this case the recycling cavity modular gridsystem 3900 has a recycling cavity shaped to self center the linearlight source 3906. By beveling the sides of the recycling cavity andusing angled magnetic contacts 3908 and 3910, electrical contact to DCstrips 3904 and 3902 and mechanically self centering the linear lightsource 3906 can occur at the same time. Other mechanical, magnetic andadhesive means and elements, which support and center the linear lightsource 3906 in the recycling modular grid system 3900 can also be used.

FIG. 40 depicts ceiling tile 4000 with in-situ recycling cavity 4002. Inthis configuration the self cooling light panel comprising of a lighttransmitting thermally conductive 4008 containing LED packages 4010 withcontact pins 4004 and 4006 can be easily attached to the ceiling tile4000 by the end user. The contact pins 4004 and 4006 can make electricalcontact to embedded interconnects, slip-on contacts, or other contactmeans as previously described. This approach allows for reconfigurationof the lighting within a suspended ceiling. In general it is preferredthat in-situ light recycling cavity 4002 has the highest reflectivitypossible but a reflectivity greater than 90% is preferred, with greaterthan 95% most preferred. White paint, polymeric coatings, metal foils,and combinations of both may be used for in-situ recycling cavity 4002.

FIG. 41 depicts suspended ceiling modular system with in-situ lightrecycling cavity grid 4100 and light emitting units 4106 and dummy units4102. Light emitting units 4106 contain LEDs and/or LED packages 4108and contacts 4110 on the light transmitting thermally conductive element4103. An interconnect and any additional active elements as previouslydisclosed (not shown) are also included. Dummy unit(s) 4102 willtypically only comprise light transmitting thermally conductiveelement(s) 4109 and contacts 4104. These dummy units serve as spacersand/or decorative elements. However additional components providingadditional functions including but not limited to power conditioning,electrical filtering, sensors, detectors, emitters, antennas, and otheractive and passive may also be incorporated into these dummy lightsources.

FIG. 42 depicts a self cooling solid state light source withreflector/thermal barrier 4206. By making the reflector 4206 out of alow thermal conductivity material such as a polymer, porous ceramic, orglass material with a thermal conductivity less than 1 W/mK the selfcooling light sources can be attached to surfaces which are thermallysensitive. The thermal isolation may be created using porosity, lowthermal conductivity materials, heat shields and other thermal barriermeans. In the case of polymers the reflector 4206 can be formed via blowmolding, injection molding, thermal forming, and other fabricationtechniques known in the art. As previously stated high reflectivity ispreferred. Most preferably the reflectivity of the reflector/thermalbarrier 4206 should be greater than 95%. Also the use of non-flammableor low flammability materials is preferred for the reasons previouslystated. Contacts 4204 and 4202 can be molded in or pressed into themolded reflector/thermal barrier 4206. Translucent light transmittingthermally conductive element 4200 provides cooling and physical supportto LEDs and/or LED packages 4210 and interconnect 4208 as previouslydisclosed. The use of this approach allows for a higher temperatureoperation point for the translucent thermally conductive element 4200than those approaches disclosed which allow for greater thermal transferto the reflector/thermal barrier 4206. This increases the lumens outputper surface area and also increases the lumens per gram. It should beapparent that reflector/thermal barrier 4206 should be made of materialcompatible with the temperatures created by this approach. Again in thisembodiment the emitting surface and cooling surface are bothsubstantially the same.

FIG. 43 depicts snap fit linear light sources for grids, undercounter,aircraft, and ceiling lighting. Housing 4300 provides mounting of theself cooling light source 4310. The self cooling light source 4310 isconstructed as previously described wherein the emitting surface(s) 4312is the heatsink. As shown the housing 4300 contains two housing contacts4302 and 4304 which form an electrical connection with light sourcecontacts 4308 an 4306 which provide power to self cooling light source4310. Housing 4300 may be made out of a wide range of materialsincluding polymers, metals and ceramics. Thermally insulative materialsare preferred to thermally isolate the self cooling light source 4310from any wood, paper, drywall or other heat sensitive materials to whichthe housing 4300 is mounted. Housing 4300 may be mounted using screws,adhesives, pins, snaps or other mechanical or chemical means. Becausethe self cooling light source 4310 does not require additionalheatsinking to dissipate its heat, housing 4310 may be made out of anymaterial which can handle the surface temperatures of the self coolinglight source 4310. Housing 4310 may also include additional support inthe form of rails, clips, Velcro, magnets, or springs which secureand/or position the self cooling light source 4310 with the housing4310. Housing contacts 4302 and 4304 and light source 4308 and 4306 mayinclude spring loaded contacts, snap fit, conductive Velcro, magnetic,or locking means to ensure electrical contact.

FIG. 44 depicts a thermally insulated lambertian self cooling lightsource with an integral thermal barrier 4400, which additionally acts asa mounting fixture. Mounting elements 4410 and 4414 can include but arenot limited to tabs, rails, spring loaded elements, clips, Velcro,adhesive strips, magnets or other mechanical/chemical means ofattachment and/or alignment. Optionally additional reflective layer 4402may be used to enhance the reflectivity of the integral thermal barrier4400 such that the recycling cavity 4408 will efficiently spread thelight from at least one LED 4404 throughout the light recycling cavity4408. Again the light transmitting thermally conductive element 4406allows for both efficient emission of the light from the at least oneLED 4404 and removing the heat generated by at least one LED 4404.

FIG. 45 depicts various connector arrangements for a self cooling lightsource with a reflector. FIG. 45A depicts two overlapping reflectorelements 4506 and 4512, which are electrically isolated by dielectriclayer 4510. The reflectors 4506 and 4512 have optional contacts 4502 and4508 respectively. Electrical power is provided through the overlappingreflectors 4506 and 4512 to the translucent thermally conductive element4500 through board contacts 4514 and 4516 which may include conductiveepoxies, clips, solder joints, through holes, wires, and/or otherconnection means. The electrical power is distributed to the at leastone LED 4504 as previously disclosed via an interconnect means (notshown).

FIG. 45B depicts another version of split reflectors 4538 and 4540 bothof which have integral contacts which mechanically and electricallycontact translucent thermally conductive element 4542 which contains atleast one LED 4544. Optionally, reflector contacts 4532 and 4534 may beused to improve the electrical contact to an external power source.Insulating bridge element 4530 serves not only to electrically isolatethe split reflectors 4538 and 4540 but also to provide support for theoverall assembly.

FIG. 45C depicts the use of side clips 4562 and 4560, which mechanicallyhold reflector 4564 and translucent thermally conductive element 4568together and thereby form the recycling cavity around at least one LED4566. In this configuration the side clips 4562 and 4560 also serve asthe electrical contact to the external power supply (not shown). Also inthis configuration reflector 4564 is most preferred to be electricallyinsulating. Alternatively, the side clips 4506, 4562 may have adielectric or insulating layer on their inside surfaces 4561 and 4563where they contact the reflector 4564. The clips may also allow fordiffering thermal expansion between reflector and light transmittingthermally conductive element. The use of any of these connection meansto form light sources with multiple translucent light transmittingthermally conductive elements 4568 is also an embodiment of thisinvention. In general, robust large contact area connections arepreferred. Multiple contact points are preferred to single pointconnections for improved reliability. The use of corrosion resistantcoatings such as tin alloys, carbon based contact, and otherenvironmentally stable layers to enable reliable electrical connectionsare also embodiments of this invention.

FIG. 46A depicts another embodiment of a light recycling cavity 4600comprising a strongly light scattering and light transmitting thermallyconductive element 4616 one which interconnects 4620 and 4618 are formedas previously disclosed. It should be noted that while the side viewshows interconnects 4620 and 4618 covering the inner surface of stronglyscattering light transmitting thermally conductive element 4616 withonly a small gap 4629, in most application standard line widths oftypically 100 micron wide and 5 microns thick would be used such thatthe amount of conductive material used is minimized. Therefore, theinterconnect only covers a small fraction of the total area of theinward facing surface 4603 of the light transmitting thermallyconductive element 4616. The width and thickness of the interconnect canbe adjusted as would be appropriate for the at least one LED orsemiconductor device 4622 based on maximum drive current and the lengthof the traces. Most preferred are interconnects 4620 and 4618 which arethin traces due to the cost of the metal materials used. Most preferredis low surface roughness silver thick film pastes with a RMS roughnessless than 5 microns. An example is Heraeus silver thick film pasteCL80-9364 which enables the use of direct attach LED die 2810 such asDA-500 die produced by Cree. Direct attached die and/or soldered LEDpackages are preferred devices for at least one LED or semiconductordevice 4622 due to the elimination of wirebonding costs. In general,high reflectivity and high conductivity materials are preferred forinterconnects 4620 and 4618.

Additional wavelength conversion elements 4624 may be placed on the atleast one LED or semiconductor device 4622 or elsewhere within the lightrecycling cavity 4600. For example on the surfaces which make up thelight recycling cavity: reflectors 4612 and 4614, flex layer 4602,interconnects 4620 and 4618, and strongly scattering thermallyconductive element 4616. External contacts 4610 and 4608 may attach tothe reflective flex circuit comprising reflectors 4614 and 4604respectively and optionally to flex layer 4602 using conductive epoxy,soldering, ultrasonic bonding, tab bonding, mechanical means, and otherconnection means known in the art. Adhesive insulators 4604 and 4606 areoptionally used to support external contacts 4608 and 4610 respectively.Similarly reflector 4612 and 4614 may make electrical contact withinterconnects 4620 and 4618 respectively using but not limited toconductive epoxy, soldering, ultrasonic bonding, tab bonding, mechanicalmeans and other connection means known in the art. A single layerreflective flex circuit is shown comprising reflectors 4612 and 4614 andflex layer 4602. However, additional layers of interconnect as practicedin the flex circuit industry may be used.

Unlike interconnects 4620 and 4618, it is most preferred that reflectors4614 and 4612 cover the majority of flex layer 4602. In addition it ismost preferred that reflectors 4614 and 4612 have reflectivity greaterthan 90%. The resulting reflective flex circuit and its use in lightrecycling cavities is an embodiment of this invention. External contacts4610 and 4608 are disclosed as pins however other means including butnot limited to clips, pads, strips, and other mechanical contact meansmay also be used. A preferred embodiment is continuation ofinterconnects 4618 and 4620 outside inner surfaces of the lightrecycling cavity 4600 such that external contacts 4610 and 4608 may bemoved to edge of the light source (not shown). These approaches and thedimensional properties of interconnects 4618 and 4616 are common to theother embodiments in this disclosure. The use of adhesives, clips,solders, mechanical means, and fusion processes to bond the variouspieces of the light source together are also disclosed.

Once formed this embodiment can create a wide range of colors when lit(by using different color LEDs or wavelength conversion elements), whilestill maintaining a substantially white body color because of thestrongly scattering nature of the strongly scattering light transmittingthermally conductive element 4616. In addition, the reflectors 4614 and4612 as well as other elements within the light recycling cavity 4600contribute to the body color of the light source. Especially in the caseof ceiling tiles and grid applications, the ability to create thinlightweight solid state light source with body colors which closelymatch the white tiles is a benefit. The desire is to essentially concealthe lighting in the ceiling structure so that unlike conventionaltroffers and can lights the lighting does not draw attention to itselfin the eyes of the occupants but instead presents a monolithic uniformceiling even though lighting fixtures are present. In addition theability to distribute the lighting throughout the ceiling tiles and gridactually makes the lighting more efficient. Light can be positionedanywhere in the ceiling as needed unlike standard troffers which aretypically placed on very regular intervals but in concentrated clumpswhich results in the need to over light some areas to meet minimumrequired lighting levels between the troffers. As previously disclosedadditional semiconductor devices and elements may be incorporated withinand/or on light recycling light cavity envelope 4600 besides just LEDs.In addition interconnects 4620 and 4618 and reflective flex circuitcomprising reflectors 4614 and 4612 and flex layer 4602 may be used toform antennas for RFID and other communication and sensor applications.

Alumina especially can be used for the strongly scattering lighttransmitting thermally conductive element 4616. The flex circuit mayalso be used to create inductive or capacitive couplers to externalmodulated energy source eliminating the need for external contacts 4610and 4608. Additional functions which can be incorporated into these selfcooling light sources are but not limited to RFID sensing, smokedetection, ambient temperature detection, RF emitters, strobe sources,optical data links, motion sensors, and wireless communications. Aslighting is required in virtually all occupied spaces it is only naturalthat sensor, communication, and security functions be integrated intothe light sources. The ability to use commercial grade low cost aluminaprovides an ideal substrate for integrating these extra electricalcomponents into the light source. The strongly scattering white bodycolor of these light sources allow for the concealment of securityfunctions such as cameras and sensors. As an example a piezo-electricspeaker can be placed within, built into or otherwise attached to thelight source. Audio and other low frequency modulation may be broughtinto via the external contacts 4608 and 4610 or separate leads. Audiomodulation in particular can be run in parallel, separately, or filteredoff the DC input or be brought in on separate inputs. The benefit ofthis approach is elimination of speakers within the ceiling and theadded benefit of enhanced cooling of the light source based on surfaceboundary interruption created by vibrations from the integrated speaker.Internal speakers can also move air into and out of the light recyclingcavity 4600. This approach also allows for easy repositioning of audiospeakers in a ceiling. The use of this approach to noise blank, createaudio ambience, create background noise, act as an audio fire warning,acoustical source for motion detection, create a distributed speakersystem, create a distributed music system. In general, this approachallows field installable, field replaceable, and field adaptable audiosystems integrated into the lighting.

As an example, a store owner could buy a light source based on thisdisclosure, which queried RFID tags at the exit from the story while anexternally identical light source could be detecting motion elsewhere inthe store. In this manner, lighting and security become the same elementreducing cost, concealing the security, and improving the aesthetics.Interconnects 4618 and 4620 may be single circuits as shown or multiplecircuits. The extra functions may be powered separately and in tandemwith at least one LED or semiconductor device 4622. Light recyclingcavity 4600 may be air, a gas, a liquid, a phase change material, anoptical transmitting solid, or combinations of both. Most preferred isair. In the case where non-homogenous materials are used to makestrongly scattering thermally conductive element 4616 air may flow intolight recycling cavity 4600. An outer porous scrim layer may optionallybe used to further modify the external body color of the source. FIG.46B further depicts a flex circuit version of the self cooling lightsource. Light recycling cavity 4662 is formed by inner reflector element4660 and translucent thermally conductive element 4664 as previouslydisclosed. In this case inner reflector element 4660 is electricallyinsulated by adhesive layer 4658 from conductive strips 4656 and 4657.In this manner conductive strips 4656 and 4657 can be used to makeconnection to interconnect 4670. Solder coated copper ribbon as used inthe solar industry is a preferred material for conductive strips 4656and 4657. Again LEDs and/or semiconductor devices 4668 and 4666 andinterconnected using interconnect 4670. Additional electrical isolationmay be provided using underfill 4672 and overcoat 4674. Paralyene andother transparent dielectric environmental coating are preferredmaterials for overcoat 4674. It should be noted that alumina and othermaterials while strongly scattering in the visible region are almosttransparent in the infrared and therefore imaging at these longerwavelengths is possible from within the light recycling cavity 4662. Theability to hide detection, security, acoustical, and other sensorfunctions within the self cooling light sources or dummy elements aspreviously disclosed in FIG. 41 is a preferred embodiment of thisinvention.

In general, the light sources disclosed may be used to attach, mount orotherwise adhere to a variety of surfaces. While halogen andincandescent sources can have surface temperatures exceeding 1500 C itis preferred that the sources disclosed in this invention operate below900 C. Even more preferably the sources disclosed herein operate below700 C. Typically building codes limit direct contact to combustiblesurfaces such as wallpaper to less than 900 C. As such incandescent andhalogen sources must be thermally isolated from these materials. Basedon the higher efficiency of solid state light sources, with the lightemitting surface being the cooling surface, the efficiency of thisinvention, and the thermal spreading of the light transmitting thermallyconductive element; 4 inch×4 inch panel lights based on this inventioncan emit in excess of 1000 lumens without exceeding the 900 C surfacetemperatures in contact with any mounting surfaces. As such the lightsources disclosed can emit a useful level of output directly mounted onwallpaper and other combustible surfaces unlike incandescent and halogensources. This allow for a wide range of applications. The non-flammablenature of the materials used in this invention do not allow for flamespread even up to 10000 C unlike prior art organic based waveguideapproaches. If even higher lumen outputs are required the thermalbarrier 4650 may further thermally isolate the heat generated in thelight source from coupling to any surface to which the light source isattached. The thermal barrier 4650 may comprise polymers, fiberglass,ceramics, or metals. The thermal barrier 4650 may also be decorative,supportive, or even form a hermetic or environmental seal for the lightsource.

FIG. 47 depicts multiple or plurality of light sources and/or dummyelements connected together to form linear, shaped or large planar arealight sources. FIG. 47A depicts light transmitting thermally conductiveelements 4712 and 4714 on which an electrical interconnect means 4710and 4708 is formed. Reflector 4704 may be separate reflectors for eachsegment of the light source or a single larger reflector that bridgesthe translucent light transmitting thermally conductive elements 4712and 4714. Jumper 4702 may comprise but not limited to flex circuits,wires, pins, mechanical clips, ribbon, or other electrical connectingmeans. Jumper 4702 may further have a contact 4700 which may comprisebut not limited to magnets, pins, clips, or other contact means known inthe art. While not shown reflector 4704 has sides as previouslydisclosed which form a light recycling cavity 4706 as also previouslydescribed. Jumper 4702 may be within the recycling cavity 4706 oroutside the recycling cavity 4706 formed by reflector 4704 and thetranslucent thermally conductive elements 4712 and 4714. Jumper 4702 mayor may not be physically attached to reflector 4704. Reflector 4704 mayor may not be part of the electrical connections used to provide powerto the LED die or packages (not shown) within the light recycling cavity4706. While a two dimensional rendering is shown, it is disclosed thatinterconnect means 4708 and 4710 cover a small portion of the surfacearea of translucent light transmitting thermally conductive elements4714 and 4712 respectively. This allows for high transmission of thelight through translucent light transmitting thermally conductiveelements 4714 and 4712 as previously disclosed.

FIG. 47B depicts multiple or plurality of light sources or dummyelements which are connected via connectors comprising of at least onepin connector 4724 and at least one socket connector 4722 which attachto interconnect means 4730 on translucent thermally conductive element4734 and interconnects means 4728 on translucent thermally conductiveelement 4732 respectively. Again reflector element 4720 forms a lightrecycling cavity 4726 along with translucent light transmittingthermally conductive elements 4734 and 4732. Using these techniquesmultiple or a plurality of light sources may be interconnectedelectrically and physically to form long linear, shaped or large arealow profile light sources without the need for heatsinks or othercooling means. In general, the techniques listed above allow for lightsources, which emit greater than 30 lumens per gram. This high lumenoutput to weight ratio and the ability to cool using substantially onlythe light emitting surface is fundamental to this invention as itreduces the material costs of lighting fixtures, allows for directapplication of solid state lighting to suspended ceilings and a widevariety of surfaces, and in many cases eliminates the need foradditional fixture elements. As an example a 1000 square foot roomrequires 30,000 lumens to provide adequate lighting levels for generalusage. Using the light sources of this invention the entire lighting forthe room will weigh less than 1 kg. This allows for direct attachment tosuspended ceilings without the need for additional support wires to thedeck. It also reduces shipping costs and storage costs. Unlikeincandescent or fluorescent bulbs the low profile and low voltagecharacteristics of these solid state light sources eliminate in manycases the need for additional fixture elements further reducing costs.

In particular the use of these light sources embedded in, attached to,or mounted to sheetrock, ceiling tiles, wood paneling, painted surfaces,metal surfaces, trim elements, brick, stone, tile or other constructionmaterials to provide lighting or intelligent lighting in homes, offices,restrooms, manufacturing, or other lighting applications is anembodiment of this invention. Intelligent lighting is also a preferredembodiment allowing for the integration of color tuning, lightharvesting, security, motion detection, or other sensor functions intothe lighting modules. As lighting is required in virtually all locationswhere humans work, reside, or occupy; the integration of sensors intothe lighting system is preferred.

The lighting system disclosed in this invention enables a low cost,simple architecture for implementing intelligent lighting. Not only arethe light sources disclosed lightweight, efficient, and cost effectivethey are also (especially in the cases where alumina is used for thetranslucent light transmitting thermally conductive elements 4734 and4732) completely compatible with multi-chip module technologies such asthick film and lithographic based electronic packaging. The keycomponent of the light source which acts as both the light emitting andcooling element also is compatible with thick film and lithography basedinterconnect means. This permits the light emitter to alsosimultaneously act as a substrate for multi-chip elements, passiveelements, or active elements and is a preferred embodiment of thisinvention. Alumina is a preferred material due to its high scatter yetlow optical absorption, white body color to external light, nearlylinear optical absorption across the visible spectrum, high transmissionin the IR, high emissivity, reasonable thermal conductivity, low cost,availability in thin sheet form, volume manufacturing, compatibilitywith high temperature thick film processing, low thermal expansioncoefficient, insulative properties, non-flammability, low moistureuptake, vacuum tightness, and dielectric properties allowing for highfrequency elements. While other materials may be used the aboveproperties all effect final product performance and must to be takeninto account. Other materials disclosed such as organic/inorganiccomposites offer advantage of lower density and wider range of bodycolor but lower operation temperatures. Holey metal approaches requirethe use of dielectric layers but allow for a wide range of aestheticfinishes since the outer surface no longer effects the light recyclingcavity performance.

FIG. 48 depicts a means to form a contiguous barrier with lighting witha retrofit system based on self cooling light sources disclosed in thisinvention. This approach overcomes the need to replace the existing gridin a suspended ceiling. This is field installable unlike the DC FlexZonesystem described previously which requires the existing grid to beremoved and replaced. In this embodiment the existing grid 4812 isattached the deck 4800 via suspension wire 4804 and mount 4802. Ceilingtiles 4804 and 4818 are suspended via the existing grid 4812. Clip onpower rail 4814 attaches to existing grid 4812 via but not limited toone of the following means, clips, adhesive, magnets, screws, snaps, orother mechanical means. Power leads 4808 and 4806 attach to contacts4816 and 4814 respectively. Power leads 4808 and 4806 may or may not beintegrated into clip on power rail 4814. Power leads 4808 and 4806further attach to at least one external power source (not shown) anddeliver power to the contacts 4816 and 4814 respectively. The lightsource 4826 contains contacts 4822 and 4824 which mate with contacts4816 and 4820 respectively. Contact 4822 and 4824 may also providemechanical, magnetic, adhesive, Velcro, or other physical attachmentmeans to hold light source 4826 to clip on power rail 4814 which in turnis attached to existing grid 4812.

The advantage of this approach is that existing grids and ceiling tilescan be used, lighting and intelligent lighting functions can be addedonly where needed, the existing grid can be cosmetically covered, theretrofit system can be installed by the end customer (especially for lowvoltage (less than 30 VDC)), it is easily removed, moved, upgraded, orotherwise changed, and the lightweight nature of the approach does notdegrade seismic performance of the ceiling. Alternately, the lightsource 4826 may be integrated in the ceiling tiles 4818 and/or 4810instead or as well as the existing grid 4812. In the case where thelight source 4840 is mounted or embedded in ceiling tile 4818, wires4842 (only one wire shown) would contact power leads 4808 and 4806 usingcontact means 4844 and 4850 as previously described. In this case bothpositive and negative inputs could be on one or each side of theexisting grid 4812 and two or more contacts 4844 would be used toprovide power to the light source 4840. Again the main advantage is thelight weight (greater than 30 lumens per gram) and the self coolingnature of this invention. Ceiling tiles 4818 are typically composed ofrecycled paper and as such contain combustible materials. They also arespecifically designed to have low thermal conductivity to isolate theplenum side 4832 from the occupant side 4834 to enhance the workenvironment for the occupants 4830. As previously state the high lumenper gram (greater than 30 lumens per gram) enables the delivery of over30,000 lumens into a room with less than 1 Kg of additional weight tothe suspended ceiling from the light sources 4826.

The light sources 4826 also cools itself substantially using the lightemitting surface dissipating the heat it generates into the occupantside 4834 of the installation. Light source 4840 similarly dissipatesits heat into the occupant side 4834 of the installation whilemaintaining a maximum surface temperature against the ceiling tile 4818of less than 900 C and even more preferably less than 700 C. Both lightsource 4822 and 4840 can deliver greater than 100 lumens of diffusesubstantially lambertian light per square inch of emitting surface whilemaintaining these surface temperature constraints. Unlike conventionalsolid state lighting this approach minimizes the amount of materialrequired to create a high lumen output distributed substantiallylambertian solid state source, minimizes the amount of weight requiredto generate 1000 s of lumens of output and does this in a package thisis less than 1 cm thick and even more preferably less than 5 mm thick.This thin package enables the formation of a nearly monolithic suspendedceiling wherein ceiling tiles 4818 and 4810 can be tegular as shown.Light source 4826 because of its thinness (less than 1 cm morepreferably less than 5 mm) can have its emitting surface 4850substantially flush with the occupant side 4852 of ceiling tile 4818.This creates a more pleasing and aesthetic look for the occupant 4830.In general, 30,000 lumens can be delivered into a room using less than 1Kg of light sources 4826 while dissipating less than 500 watts. A 1000square foot room would be illuminated with greater than 30 lumens persquare foot while maintain a maximum surface temperature of less than900 C and even more preferably less than 700 C. The low thermalresistance of the approach also maintains the LED junction temperatureswithin light source 4826 to be only a few degrees higher than theemitting surface 4850. Further still, the high lumens per gram output oflight source 4826 enables clip, snap, mechanical, Velcro, adhesive andmagnetic suspension and mounting to the ceiling. Typically the existinggrid 4812 is steel as such magnets can be used to not only hold contacts4816 and 4820 to contacts 4822 and 4824 respectively, magnets may beused to hold light source 4826 in place.

FIG. 49A depicts a means to form a barrier 4900 of this inventionutilizing a retrofit wall or floor installation of the light sources4902. Because additional elements such as heatsinks, diffusers, orframes are not needed with the disclosed light sources 4902 for use as afixture, light source 4902 can be mounted onto any surface whichcontains some power input means 4904 and 4906. Power input means 4904and 4906 may include but not limited to embedded wires, tape basedconductors, TCO based conductors, inductive coupling means, capacitivecoupling means and radiative coupling means. As previously statedbecause the preferred embodiment is alumina for the emitting and coolingsurfaces a wide range of active and passive elements can be easilyincorporated into the light source 4902. As an example power input means4902 and 4906 may be simply two copper conductors embossed, trenchedinto, or otherwise embedded into wall or floor barrier 4900.

As shown in FIG. 49B power input means 4904 can be covered by coverlayer 4912 which may include but not limited to wallpaper, spackle,paint or other coverings. Because light sources 4902 can deliver over500 lumens in an area of less than 10 square inches, weigh less than 20grams, in a package less than 5 mm thick, and still maintain a surfacetemperature less than 900 C while dissipating substantially all the heatgenerated into the room via the light emitting surface, it is possibleto simply mount the light sources 4902 to the wall or floor 4900 usingmechanical means such as but not limited to screws, pins, staples,magnets, Velcro, adhesives and other attachment methods. As shown inFIG. 49B the support pin 4908 may also act as an electrical connectionbetween light sources 4902 and power input means 4094, even piercingcover layer 4912. Essentially the lightweight nature of these lightsources 4902 can be tacked on to wall or floor 4900 if the proper powerinput means 4904 and 4906 are provided either within, on, behind, infront of, or attached to wall of floor 4900. While two leads are shownfor power input means 4904 and 4906 multiple lines may be used forcontrol and even digital or RF inputs. Again light emitting and dummyunits can be used in floor and wall applications as well. The lightsources disclosed are applicable for indoor, outdoor, underwater,hazardous environment, space, and pressurized installations. Low voltage(less than 30 VDC) are preferred due to elimination of shock hazardshowever AC and higher voltages are disclosed with the addition ofdielectric protection and other safety features known in the industry.Low voltage drive is also preferred due to elimination of AC to DCconversion losses for intelligent lighting functions which usuallyoperate using DC. Using this approach wall wart power supplies anddirect attachment to solar and other renewable resources are envisionedand preferred.

FIG. 50 depicts a means of forming a barrier of this invention utilizingmodular sheathing units with integrated low voltage conductors to form alow voltage power grid for existing walls and floors. Sheathing unit5000 contains at least two conductors 5016 and 5014. Sheathing unit 5000may comprise but not limited to composite, paneling, sheetrock, andother construction materials. Sheathing unit 5000 most preferably is notpermanently affixed to underlying walls and floors 5020 and issubstantially self supporting. In a manner similar to modular flooringwhich snap together sheathing unit 5000 is intended to be removable suchthat the modular system can be taken with the owner when they move. Themodular nature also allow for easy remodeling and redecorating withoutdisturbing the underlying walls and floors 5020. While attachment tounderlying walls and flooring is possible it is not preferred. Thisenables the end user to easily reconfigure the room as required. As suchsheathing unit 500 has sufficient structural integrity to support itselfsubstantially over the typical 8 foot floor to ceiling distance withattachment only at the top and bottom to underlying walls and floor5020. Most preferably sheathing unit 5000 has an integral ornon-integral locking system which allows the multiple sheathing units5000 to be linked together. The multiple sheathing units 5000 may or maynot contain at least two conductors 5016 and 5014 in each unit. At leasttwo conductors 5016 and 5014 are shown with contact leads 5006 and 5004respectively, which connect to a main low voltage power distributionsystem (not shown). The main low voltage power distribution system maybe hidden within trim molding, wainscoting, or other covering meanswhich may also be attached or mounted to the assembled sheathing units5000 after installation.

Contact leads 5006 and 5004 may also be attachment means for securingsheathing units 5000 to the underlying floors and walls 5020. Thesheathing units 5000 may also extend to ceilings or be freestandingelements as well. Connector means 5010 and 5008 are meant toelectrically connect to at least two conductors 5016 and 5014 to providepower to panel light 5002. Connector means 5010 and 5008 may optionallyprovide for attachment means of panel light 5002 to the sheathing unit5000 as well. The lightweight, elimination of heatsink, and thinness ofthe panel light 5002 disclosed previously enables the use of this typeof independent modular low voltage power grid. In conventional solidstate lighting the underlying walls and floors 5020 would be drilled orotherwise punctured to allow for electrical wiring or recess mounting ofthe heatsink or other cooling means. This not only means that anychanges such as moving a light source results in have to patch orotherwise repair the underlying walls and floors 5020 but it also meansthat underlying walls and floors 5020 no longer provide a continuousbarrier which compromises the thermal and fire performance of the room.By creating an outer modular sheath comprising of multiple sheathingunits 5000 which contain integral low voltage power grids the end usercan change, remove, take with, or otherwise modify any room. While theapproach can be extended to the ceiling as previously disclosed thesheathing units 5000 may require addition support or mounting elementsto prevent warping. Sheathing units 5000 may also be used to connect,distribute or otherwise connect the low voltage power grid between thefloor, ceiling, or walls. In this manner, a single power supply may beused to provide power to multiple lighting source or other devices suchas but not limited to audio, air movement, displays, floor lamps,kitchen appliances, or tools.

An example, of additional support or mounting elements for ceilingmounting would be but not limited to the suspended grid, attachment torafters, or other methods consistent with mounting of ceiling tiles,paneling, or sheetrock. Sheathing units 5000 may also be spaced out fromunderlying walls and floors and be acoustically permeable such thatadditional noise dampening can be created compared to hard mountedapproaches. Sheathing units 5000 spaced a distance from underlying wallsand floors 5020 may also provide air channels for HVAC. Hot air may berouted to closer to the floor and cold air may be routed to the ceilingusing the space between the sheathing units 5000 and the underlyingwalls and floors 5020 to create more efficient heating and cooling.Alternately, radiant heating and/or cooling units may be incorporatedinto sheathing units 5000, between sheathing units 5000 and underlyingwalls and floors 5020, and/or attached to underlying walls and floors5020 such that sheathing units 5000 act to not only hide the radiantheating and/or cooling units but also serve to enhance air circulationby forming induced draft air channels. In general, a preferredembodiment is a semi-rigid substantially freestanding modular systembased on multiple connected sheathing units 5000 where at least onesheathing unit 5000 contains at least one low voltage power distributiongrid.

FIG. 51 depicts at least one panel light 5112 mounted to at least onemodular sheathing unit comprising of an inner dielectric layer 5104, atleast one inner conductor layer 5102, and at least one outer dielectriclayer 5100. In this embodiment the modular sheathing unit is shownagainst wall, floor, or ceiling 5106. As previously stated the at leastone modular sheathing unit is preferably substantially freestanding suchthat the power grid can be easily reconfigured, replaced, changed andmoved to a new location. In the figure outer dielectric layer 5110 ispierced by contact probe 5110 to electrically connect the panel light5112 to the inner conductor layer 5102. Multiple contact probes 5110would be used to provide power to panel light 5112. Alternately, outerdielectric layer 5100 may be removed via mechanical, chemical, orabrasive means to expose inner conductor 5102 to enable electricalcontact to panel light 5112. Alternately, inductive and capacitive meansmay be used to transfer power between inner conductor 5102 and the panellight 5112. In the wireless power transfer case a transmitting elementwould be additional incorporated into the sheating unit and receivingunit would be incorporated into the panel light 5112 as previouslydisclosed. Additional mounting means 5114 may include but not limited toscrews, adhesive, clips, nails, tape, magnets, Velcro, or other mountingmeans. The light weight of the disclosed panel lights 5112 enables theuse of this approach without the need for additional support viaattachment walls, floor, or ceiling 5106. Additional trim, reflectors oroptical elements both functional and decorative may be further attachedto the outer dielectric layer 5100 and/or panel light 5112. The panellight 5112 emits both light and heat to the ambient environment 5108.

FIG. 52 depict a room comprising wall 5202, ceiling 5220, and floor 5228with low voltage devices 5218, 5204, 5210, 5214, and 5216 all powerusing power legs 5226, 5222, 5206, 5208, 5212, and 5224 off the main lowvoltage power grid 5200. In some cases the power leg directly attachesthe low voltage device to the low voltage power grid 5200. In othercases, multiple power legs which are 3 dimensionally oriented relativeto each other are used to supply power to the low voltage device. Anexample is low voltage device 5218 which is connected to the main lowvoltage power grid 5200 via power legs 5222 and 5218. Low voltagedevices 5218, 5204, 5210, 5214, and 5216 may comprise but not limited topanel lights, smoke detectors, motion sensors, light sensors,temperature sensors, DC to AC converters, DC to DC converters, datalinks, security sensors, RFID sensors, audio devices, video devices,entertainment devices, tools, kitchen appliances, and timers. In thisembodiment sheathing units containing low voltage power grids areinterconnected substantially orthogonally as shown howevernon-orthogonal interconnects between sheathing units is also envisioned.In general, it is disclosed that substantially freestanding modularsystem of sheathing units containing low voltage power grids areinterconnected such that substantially only openings 5230 are notcovered by the sheathing units. Openings 5230 may include windows,doors, central vacuum outlets, and HVAC openings. This box within a boxallows for a high degree of flexibility and allows for HVAC, radiantheating, and cosmetic issues to be easily covered and/or hidden. As anexample, an apartment with an unfinished concrete block wall can beretrofitted with wood paneling with an embedded low voltage power gridwhich can be removed by the tenant at the end of the lease using thisapproach in a manner very similar to how snap and lock floating flooringcan be reused. This minimizes material waste associated withredecorating and renovation. Low voltage power grids do not requireelectrician installations, this coupled with light weight self coolingpanel lights enables the reusable modular sheathing approach disclosed.

FIG. 53A depicts a reflective grid comprising of a grid element 5304 andreflector element 5306 which form part of the light recycling cavity. Inthis embodiment the end user installs the light transmitting thermallyconductive element 5300. The light transmitting thermally conductiveelement 5300 may be attached to the grid element 5304 to form the lightrecycling cavity using but not limited to at least one of the followingelements, clips, pins, magnets, adhesives, Velcro, or other mechanicalmeans. The translucent thermally conductive element 5300 may furthercontain at least one of the following associated elements 5308, asemiconductor device, passive element, and/or light source. Thetranslucent thermally conductive element 5300 may also be a dummy unitdesigned to provide a particular aesthetic look. This embodiment isenabled because the heat is removed and dissipated using thesubstantially only the translucent thermally conductive element 5300.This allows the reflector element 5306 be a wide range of materialsincluding but not limited to reflective plastics, reflective metals, andother reflective coatings which may be attached or applied to the gridelement 5304. This embodiment further reduces the weight of the lightsource which must be provided to the end user. Greater than 100 lumensper gram is possible when only the translucent thermally conductiveelement 5300 and any associated elements 5308 are all that is requiredto be shipped to the end user. This embodiment further reduces the costof shipping and stocking. In addition this embodiment allows the enduser access to the associated elements 5308 for upgrades and retrofits.As an example, wireless data links could be added or upgraded simply byreplacing associated elements 5308 as required. This user adaptabilityis an embodiment and benefit of this invention. Given the long life(greater than 10 years) of solid state lighting this approach ifstandardized would allow for the end user to take their lighting to anew location as well as reconfigure the present location. FIG. 53Bdepicts a light transmitting thermally conductive element 5322 withassociated elements 5324 which may include but not limited to lightsources, active semiconductor elements, passive electronic elements, andmicrowave and RF elements. The light transmitting thermally conductiveelement 5322 forms the aperture element for a recycling cavity byattaching the light transmitting thermally conductive element 5322 tomounting surface 5320 which may include but not limited to a ceilingtile, wall, floor, ceiling, wood element, plastic element, sheetrock,painted panel, glass sheet, or other surface. The mounting surface mostpreferably has a reflectivity to light or radiation emitted fromassociated elements 5324 greater than 90%. The attachment may be viapins, wires, adhesives, mechanical means, nails, screws, clips, or otherattachment means.

FIG. 54A depicts a light recycling light source with holey lighttransmitting thermally conductive element 5402. The reflector 5400 formsthe light recycling cavity. The lens elements 5403 are aligned to theholes with the holey light transmitting thermally conductive element5402 such that the solid angle of the light emitted from the lightrecycling light source is reduced to less than lambertian. This can beused to reduce glare and/or form a directive light source.

FIG. 54B depicts a recycling light source comprising a holey lighttransmitting thermally conductive element 5422 and a reflector 5420where the holes in the holey light transmitting thermally conductiveelement 5422 are not perpendicular to the light emitting surface of theholey light transmitting thermally conductive element 5422. FIG. 54Cdepicts a recycling light source comprising of a holey lighttransmitting thermally conductive element 5432 and a reflector 5430.Additional turning element 5434 may be formed when the holes are formedin the holey light transmitting thermally conductive element 5432 or beattached or adhered such that the holes within holey light transmittingthermally conductive element 5432 are substantially aligned withadditional turning element 5434.

FIG. 55 depicts a compound shaped light transmitting thermallyconductive element 5504 which can be attached to a flat or non-flatreflective mounting surface. The mounting surface 5500 may be reflectiveand may or may not be ferromagnetic or magnetic. Optional reflectivelayer 5502 may be used to enhance the efficiency of the light recyclingcavity 5518. Because the shaped light transmitting thermally conductiveelement 5504 dissipates substantially all the heat generated by LEDpackage 5506 there is no need for further heatsinking means.Interconnect 5510 and 5512 formed on the shaped light transmittingthermally conductive element 5504 make contact to conductors 5514 and5516 respectively. Conductors 5514 and 5516 may be metals, TCOs, orother conductive materials. If the mounting surface 5500 isferromagnetic or magnetic, magnetic mounts 5520 and 5522 may be used tonot only bring interconnect 5510 and 5512 together with conductors 5514and 5516 but also hold the light source physically to the mountingsurface 5500. Alternately, electrical connection may be via pins, clips,conductive Velcro, springs, screws, nails or other mechanical means. Apreferred material for conductor 5514 and 5516 is patterned ITO or otherTCO with low optical absorption to the light emitted by LED package 5506such that the light recycling cavity 5518. The reflective layer 5502 maybe a glass sheet with patterned ITO or other TCO on the surface formingthe inner surface of the light recycling cavity 5518 with a reflectivecoating on the glass surface against the mounting surface 5500.

FIG. 56 depicts a gimbal 5604 supporting a self cooling lightweightrecycling light source 5606 suspended from a ceiling 5600 or some othermounting surface using a mount 5602. In this case the gimbal 5604 andmount 5602 are greatly simplified and can be much lighter due thelightweight nature of the self cooling lightweight recycling lightsource 5606. The patient 5608 on the table 5610 can be more easilyexamined. The light source may be mounted to a variety of surfacesincluding the floor 5612. In general, the lightweight greater than 50lumens per gram and high output level of this approach allows for thedelivery of lighting into a number of weight critical lightingapplications including but not limited to, mobile, aircraft, automobile,motorcycle, bicycle, and other applications in which weight is critical.The substantially inorganic construction of this approach also providesbenefits associated with environmental resistance, color fastness, andnon-flammability. Unlike substantially organic approaches such astroffer with large plastic diffusers and polymeric waveguides approachare intrinsically heavy and susceptible to photochemical degradationfrom both sunlight and the UV/blue portion of the light emitted from theLEDs themselves.

FIG. 57 depicts a barrier comprising of at least one support gridelement 5712 supporting at least one central attachment point devices5724 to the walls 5702 and 5704. The at least one support grid element5712 may alternately be attached to the deck 5700 or floor 5722 as welldepending on the orientation of the barrier. The barrier assembly mayadditionally have support wire 5706 which is anchored to the deck 5700using mount 5708 and attached to either a central attachment pointdevice 5724 or a support grid element 5712. The reduced weightassociated with the use of self cooling lighting sources 5720 allows forthe use of substantially centrally supported barrier elements 5714.Using a substantially central mounting approach it becomes possible tolayer or stack the barrier elements 5714, 5716, and 5718. Layeringallows lighting to be hidden behind barrier elements as shown in barrierelements 5716 and light source 5726. The layered or stacked ceilingtiles 5714, 5716, and 5718 can be used to conceal lighting and otherfunctions previously disclosed. As long as there is sufficient air gapallowed between barrier elements 5714, 5716, and 5718, air can flowbetween occupant side 5730 and plenum side 5732. The centrally supportedbarrier elements 5714, 5716, and 5718 may attach to central attachmentpoint device 5724 via Velcro, mechanical means, clips, screws, snaps orlocking mechanisms. Most preferably, centrally supported barrierelements 5714, 5716, and 5718 are attached using a mounting means whichis not visible from occupant side 5730. This embodiment can be used as avery effective acoustical dampening ceiling due to sound waves beingtrapped in the plenum side 5732.

Alternately, centrally supported barrier elements 5714, 5716 and 5718may be substantially in the same plane such that a monolithic surface isformed. The centrally supported barrier elements 5714, 5716, and 5718may also have edges which interlock, snap together or otherwise attachto each other. In general, the lightweight nature of the self coolinglight sources 5720 and 5726 enables support grid element 5712, centralattachment point device 5724, and centrally supported barrier elements5714, 5716, and 5718 to be lighter weight and lower cost materials. Aspreviously disclosed the self cooling light sources 5720 and 5726 arelight recycling cavity light sources or light recycling cavity elementswhich are integrated into centrally supported barrier elements 5714 and5716 respectively.

FIG. 58 depicts a strip light based on the previously describedtechniques of this invention containing multiple translucent lighttransmitting thermally conductive elements 5800, 5802, 5804, and 5806attached to a larger reflector 5808 that form light recycling cavity5805. This allows for thermal expansion difference and a degree offlexing of the strip light. As an example, translucent lighttransmitting thermally conductive elements 5800, 5802, 5804 and 5806 maybe 500 micron thick alumina pieces which are 1 inch×6 inches. The largerand longer reflector 5808 may be coated aluminum, which is less than 300microns thick. The large reflector 5808 is used to hold the multipletranslucent light transmitting thermally conductive elements 5800, 5802,5804 and 5806 such that a substantially contiguous 24 inch×1 inch selfcooling strip light is formed. The large reflector 5808 being aluminumis more flexible than the alumina pieces allowing the strip to flex.This slightly flexible nature allows the strip light to connect tosurfaces which are not perfectly flat like suspended ceiling grids. Walland floor mountings may also require a less than rigid strip light dueto non-flat surfaces.

FIGS. 59A-E depicts a variety of self cooling recycling cavity lightsources in which the light emitting and cooling surfaces aresubstantially the same. FIG. 59A depicts a translucent lighttransmitting thermally conductive element 5900 and a reflector 5918which forms a light recycling cavity 5907 in which at least one LEDpackage 5912 is mounted to the translucent thermally conductive element5900 along with an interconnect 5908 and 5910. An LED package typicallycontains an LED mounted to a substrate with a phosphor or wavelengthconversion element covering the LED. A preferred LED package for use inthis light source is one with a small ceramic (alumina) substrate thatis surface mountable. The at least one LED package 5912 generates heatwhich is transferred by thermal conduction to the light transmittingthermally conductive element 5900 and spread out as depicted by heat ray5904 over an area greater than the area of the at least one LED package5912 and transferred to the surrounding ambient via convective and/orradiative ray 5902. Also the light emitted depicted by ray 5914 isemitted from the at least one LED 5912, is reflected off the reflector5918 as reflected ray 5916 one or more times and impinges on thetranslucent light transmitting thermally conductive element 5900 whereit is either further reflected off the interior surface 5903 of thetranslucent light transmitting thermally conductive element 5900 orbecomes transmitted ray 5906 which exits the recycling cavity 5907 fromexterior surface 5901 of translucent light transmitting thermallyconductive element 5900. Transmitted ray 5906 and heat ray 5904 travelsubstantially in the same direction and are emitted from the sameexterior light emitting surface 5901 of translucent light transmittingthermally conductive element 5900. As in other embodiments of thisinvention the light emitted rays 5916 on average experience a largenumber of reflections before exiting the recycling light cavity 5907.This creates a more uniform brightness distribution on exterior surface5901 of light transmitting thermally conductive element 5900. Ingeneral, materials which exhibit less than 20% in line transmission arepreferred to generate high uniformity. Most preferred is alumina.

FIG. 59B depicts another light recycling cavity source in which thelight emitting surface also is the cooling surface. In this case the atleast one LED die 5936 is mounted on a holey metal recycling cavity5930. In this embodiment the interconnect 5934 may also require adielectric layer 5932 to electrically isolate the interconnect 5934.Holes 5931 in holey metal recycling cavity 5930 allow for light rays toeventually exit the holey recycling cavity 5930. While there may beadditional thermal resistance from the dielectric layer 5932, the higherthermal conductivity of metals such as aluminum can more effectivelyspread the heat generated by the at least one LED package 5936 even withholes 5931. Alternately, the holey metal recycling cavity may be sintermetals, porous ceramics, porous composites, and other thermallyconductive materials which also have holes 5931 which are either randomor combinations of holes and translucent materials such as metal/glasscomposites. The basic requirement is that heat is transferred to thesame surfaces which also emit light. The heat generated by elementswithin the recycling cavity 5933 may be transferred to the lightemitting surface by conduction, convection, and radiation orcombinations of these cooling means.

FIG. 59C depicts a self cooling light recycling source is which LEDpackage 5962 is mounted within the recycling cavity 5951 but not on theinner surface 5955 of the light emitting portion of the holey recyclingcavity element 5952. Heat is conducted to exterior surface 5951 bythermal conduction ray 5966 and transferred to the surrounding ambientvia convection and/or radiative means 5950. The LED package 5962 ismounted on interconnect 5960 which in turn is isolated from the holeyrecycling cavity element 5952 using dielectric layer 5958 as in FIG.59B. In this configuration, there is an additional thermal resistanceassociated with moving the heat via thermal conduction ray 5966. Thermalinsulator 5954 may be used in this configuration to thermally isolatethe holey recycling cavity element 5952 from the mounting surface 5959.Building codes require that combustible surfaces not be exposed totemperatures greater than 90° C. By using thermal insulator 5954 theexterior surface 5951 portion of the holey recycling cavity element 5952can be greater than 90° C. and yet the light source can still be mountedon combustible surfaces by limiting the convection and/or radiativemeans 5950 to substantially only the light emitting portion of exteriorsurface 5951 of holey recycling cavity element 5952.

FIG. 59D depicts a holey light recycling cavity element 5970 in whichLED package 5974 is mounted onto circuit board 5976. The light ray 5972is still recycled multiple times within the holey light recycling cavityelement 5970 but heat from the LED package 5974 is conducted firstthrough the circuit board 5976 then transferred to holey light recyclingcavity element 5970 via conduction. The heat is then conducted again tothe light emitting portion of the holey light recycling cavity element5970. Circuit board 5976 may be a flex circuit, printed circuit board,multi-chip module, and interconnect means. In this configuration a lowthermal resistance thermal conduction path within the circuit board 5976and a low thermal resistance interface between circuit board 5976 andholey light recycling cavity element is required to move the heatgenerated by LED package 5974 to the cooling surface and light emittingsurface 5973 of the holey light recycling cavity element 5970. In theseconfigurations the intent is to provide a low thermal resistance path tothe light emitting surfaces so that substantially most of the heatgenerated within the light recycling light source is transferred to thesurrounding ambient using substantially the same surface as which lightis emitted from the light recycling light source. In general and from apractical standpoint the light emitting surfaces face the space or areato be illuminated. With the light sources of this invention all emittingsurfaces are exposed to ambient. Therefore with the light sourcesdiffuse and/or directly viewable all the light emitting surfaces can beused for convection and radiative cooling as well as light emission. Allother surfaces of the disclosed light sources not exposed to ambient canbe used for external interconnect, mounting, and can be thermallyisolated from the mounting surface if needed. This greatly increaseswhere, how, and on what surfaces or structures the light sources can beused because substantially all the cooling from the light emittingsurfaces are in convective contact with the ambient space occupied bythe end users.

FIG. 59E depicts a light recycling cavity light source in which two ormore translucent light transmitting thermally conductive elements 5986and 5988 and reflectors 5996 and 5984 form the light recycling cavity5991. The LED packages 5990 and 5986 are mounted within the lightrecycling cavity 5991. Rays 5994, 5992, and 5982 are emitted from thelight recycling cavity 5991 through the two or more light transmittingthermally conductive elements 5986 and 5988. The reflectors 5996 and5984 may be holey, solid, or substantially porous. The reflectors 5996and 5984 may also be thermally insulated as discussed in FIG. 59C. Ingeneral, combinations of light emitting surfaces which are also coolingsurfaces such as two or more light transmitting thermally conductiveelements 5986 and 5988 may be combined with opaque reflectors such asreflector 5996 and 5984 which may or may not contain thermal barriers orother thermal isolation means to allow for safe mounting of thedisclosed light sources to combustible surfaces. This allows for highlumen output light sources to be integrated into or attached to but notlimited to ceiling tiles (even if those ceiling tiles are thermallyinsulating and constructed of combustible materials like recycledpaper), sheet rock with paper outer surfaces, wallpapered surfaces,painted surfaces, fabrics, plastic surfaces, and wood surfaces. Mostpreferred is the mounting of the LED packages 5990 and 5986 on lightemitting surfaces such that the minimum thermal resistance can beachieved between the LED packages 5990 and 5986 and outer light emittingsurfaces of two or more light transmitting thermally conductive 5988 and5986. However, as described above LED packages 5990 and 5986 may bemounted anywhere within the light recycling cavity 5991 as long as theLED packages 5990 and 5986 are thermally connected to the two or morelight transmitting thermally conductive elements 5988 and 5986.

FIG. 60 depicts a light recycling self cooling light source. In thisembodiment a porous thermally conductive element 6000 contains an arrayof holes 6002. Alternately array of holes 6002 may be transmittingelements, porosity, and sintered metals. The porous thermally conductiveelement 6000 may be shaped in a variety of three dimensional shapesincluding but not limited to hemispheres, cylinders, cubes, and freeform shapes to create a desired aesthetic look. The shape of porousthermally conductive element 6000 shape and distribution of an array ofholes 6002 may also be used to create a desired far field pattern aswell. As previously disclosed the use of materials with reflectivitygreater than 90% for inner surface 6016 of porous thermally conductiveelement 6000 is preferred to maximize the efficiency of the lightrecycling cavity 6006. Concurrently, the porous thermally conductiveelement 6000 most preferably exhibits a thermal conductive of greaterthan 1 W/m/K and even more preferably greater than 30 W/m/K such thatheat generated by LED package 6004 can be spread efficiently to thelight emitting side of exterior surface 6018 of porous thermallyconductive element 6000 and be transferred to the same ambientenvironment as illuminated by the light source. In this embodiment LEDpackage 6004 is mounted onto flex circuit 6014, which contains at leasttwo conductors 6012 and 6010. At least two conductors 6012 and 6010, inadditional to providing power to LED package 6004 also provides athermal conduction path through dielectric layer 6008 to the porousthermally conductive element 6000. This embodiment can also be realizedusing translucent light transmitting thermally conductive elements forporous thermally conductive element 6000. However, the higher thermalconductivity, ease of forming and low cost of metals such as aluminumare most preferred. In addition, the use of reflectivity enhancedaluminum like Alanod™ with an array of holes 6002 for porous thermallyconductive element 6000 allows for the exterior surface 6018 to bepainted and otherwise modified to create a wide range of aestheticlooks. Most preferably, any coating on the exterior surface 6018 shouldexhibit a thermal conductivity greater than 1 W/mK and an emissivitygreater than 0.3 to enhance convective and radiative heat transfer tothe surrounding ambient environment 6020. In this case, light emittedfrom the LED package 6004 exits from the array of holes 6002 while theheat is mostly emitted off the exterior surface 6018. Some convectiveheat transfer can occur as air from the surrounding ambient environment6020 passes through the array of holes 6002 and into the recyclingcavity 6006. In this case, even LED package 6004 and the inner surfaces6016 of porous thermally conductive element 6000 may enhance heattransfer to the surrounding ambient environment 6020. In addition, thearray of holes 6002 allow for additional radiative heat transfer to thesurrounding ambient environment 6020 in a manner very similar to how thelight emitted from LED package 6004 exits the light recycling cavity6006.

FIG. 61A depicts self cooling recycling light sources with thermaltransfer elements 6106. The thermal transfer elements may includeglasses, metals, ceramics, amorphous materials, polycrystallinematerials and single crystalling materials with or without luminescentmaterials. The heat generated by LED package 6102 is transferred throughreflector 6104 through thermal transfer elements 6106 to the lighttransmitting thermally conductive element 6100 via conduction. Thethermal transfer elements 6106 may be light transmitting, wavelengthconverting, opaque, and/or translucent but most preferably the thermaltransfer element 6106 exhibit low optical losses because they are withinthe light recycling cavity 6108.

FIG. 61B depicts a substantially contiguous thermal transfer element6128 surrounded by reflective interconnects 6122 and 6124. LED die orpackage 6126 is in thermal contact with the thermal transfer element6128 which in turn transfer the heat generated for LED die or package6126 to the light transmitting thermally conductive element 6120. Inthis embodiment thermal transfer element acts as an embedded waveguideelement as well as a thermal transfer element.

While the invention has been described in conjunction with specificembodiments and examples, it is evident to those skilled in the art thatmany alternatives, modifications and variations will be evident in lightof the foregoing descriptions. Accordingly, the invention is intended toembrace all such alternatives, modifications and variations that fallwithin the spirit and scope of the appended claims.

1. A suspended ceiling system comprising: a support grid supportcomprising a plurality of intersecting struts that form a plurality ofgrid openings, the support grid supported within an internal space of abuilding; a plurality of ceiling tiles mounted to the support grid andpositioned in the grid openings to collectively form a barrier, each ofthe ceiling tiles comprising a front surface facing an occupant portionof the internal space of the building and a rear surface opposite thefront surface; at least one solid state light source comprising: atleast one reflector element; at least one light emitting diode (LED); atleast one light transmitting thermally conductive element, the lighttransmitting thermally conductive element providing a common lightemitting and cooling surface to dissipate a majority of the heat fromthe solid state light source, the common light emitting and coolingsurface facing the occupant portion of the internal space; and the solidstate light source at least partially embedded in and supported by oneof the ceiling tiles; wherein the scrim is a light transmittingthermally conductive scrim, and wherein light transmitting thermallyconductive scrim overlays the common light emitting and cooling surfaceof the light transmitting thermally conductive element to conceal thesolid state light source.
 2. The suspended ceiling system according toclaim 1 wherein the reflector element and the light transmittingthermally conductive element form a light recycling cavity; wherein theLED is mounted on the light transmitting thermally conductive element inthe light recycling cavity; and wherein light emitted by the LED isredirected within the light recycling cavity by the reflector elementand passes through and exits from the solid state light source via thelight transmitting thermally conductive element through the common lightemitting and cooling surface.
 3. The suspended ceiling system accordingto claim 1 wherein the common light emitting and cooling surface of thelight transmitting thermally conductive element acts as the primary heatdissipation means of the LED.
 4. The suspended ceiling system accordingto claim 1 wherein the entire weight of the solid state light source issupported by the one of the ceiling tiles.
 5. The suspended ceilingsystem according to claim 1 wherein the total weight of the solid statelight source and all heat sinking for the solid state light source isless than one gram per square foot yet provides greater than 30 lumensper square foot of illumination throughout an illuminated area of theoccupant portion of the internal space.
 6. The suspended ceiling systemaccording to claim 1 further comprising: the one of the ceiling tilescomprising a recess formed into the front surface of the one of theceiling tiles, the recess defined by a recess sidewall and a recessfloor surface, the recess sidewall extending from the front surface ofthe one of the ceiling tiles to the recess floor surface; and the solidstate light source disposed in the recess and mounted to the one of theceiling tiles. 7.-9. (canceled)
 10. The suspended ceiling systemaccording to claim 6 further comprising: the one of the ceiling tileshaving a thickness measured from the front surface of the one of theceiling tiles to the rear surface of the one of the ceiling tiles; therecess of the one of the ceiling tiles having a depth measured from thefront surface of the one of the ceiling tiles to the recess floorsurface of the one of the ceiling tiles; and wherein the thickness ofthe one of the ceiling tiles is greater than the depth of the recess ofthe one of the ceiling tiles. 11.-17. (canceled)
 18. The suspendedceiling system according to claim 1 wherein each of the ceiling tilescomprises a side edge extending between the front and rear surfaces andhaving a profile that engages the struts to support the entire weight ofthe ceiling tile. 19.-20. (canceled)
 21. An integrated ceiling panel andlighting apparatus comprising: a ceiling tile comprising: a frontsurface; a rear surface opposite the front surface; a side edgeextending between the front and rear surfaces of the ceiling tile; arecess formed into the front surface of the ceiling tile, the recessdefined by a recess sidewall and a recess floor surface, the recesssidewall extending from the front surface of the one of the ceilingtiles to the recess floor surface; at least one solid state light sourcecomprising: at least one reflector element; at least one light emittingdiode (LED); at least one light transmitting thermally conductiveelement, the light transmitting thermally conductive element providing acommon light emitting and cooling surface to dissipate a majority of theheat from the solid state light source, the common light emitting andcooling surface facing the occupant portion of the internal space; andthe solid state light source disposed within the recess and mounted tothe ceiling tile; wherein each of the ceiling tiles comprises a core anda scrim, the scrim comprising the front surface of the ceiling tile andwherein the scrim is a light transmitting thermally conductive scrim,and wherein light transmitting thermally conductive scrim overlays thecommon light emitting and cooling surface of the light transmittingthermally conductive element to conceal the solid state light source.22. The integrated ceiling panel and lighting apparatus according toclaim 21 wherein the recess sidewall circumferentially surrounds a sideedge of the solid state light source.
 23. The integrated ceiling paneland lighting apparatus according to claim 22 wherein the side edge ofthe solid state light source is in surface contact with the recesssidewall.
 24. The integrated ceiling panel and lighting apparatusaccording to claim 21 wherein the solid state light source comprises arear surface opposite the common light emitting and cooling surface, therear surface of the solid state light source in surface contact with therecess floor surface of the ceiling tile.
 25. The integrated ceilingpanel and lighting apparatus according to claim 21 further comprising:the one of the ceiling tiles having a thickness measured from the frontsurface of the ceiling tile to the rear surface of the ceiling tile; therecess of the one of the ceiling tiles having a depth measured from thefront surface of the ceiling tile to the recess floor surface of theceiling tile; and wherein the thickness of the ceiling tile is greaterthan the depth of the recess.
 26. The integrated ceiling panel andlighting apparatus according to claim 21 wherein the recess floorsurface is formed by a portion of a core of the ceiling tile.
 27. Theintegrated ceiling panel and lighting apparatus according to claim 21wherein the reflector element and the light transmitting thermallyconductive element form a light recycling cavity; wherein the LED ismounted on the light transmitting thermally conductive element in thelight recycling cavity; and wherein light emitted by the LED isredirected within the light recycling cavity by the reflector elementand passes through and exits from the solid state light source via thelight transmitting thermally conductive element through the common lightemitting and cooling surface.
 28. The integrated ceiling panel andlighting apparatus according to claim 21 wherein the common lightemitting and cooling surface of the light transmitting thermallyconductive element acts as the primary heat dissipation means of theLED. 29.-43. (canceled)
 44. A barrier with lighting comprising: asubstantially contiguous suspended ceiling system comprised of at leastone ceiling tile and a support grid which supports said ceiling tile; atleast one light source, the light source comprising: at least onereflector element; at least one light emitting diode; at least one lighttransmitting thermally conductive element; wherein the lighttransmitting thermally conductive element provides a common lightemitting and cooling surface to dissipate heat from the light source;and wherein said light source is either: (1) mounted directly to thesupport grid of the suspended ceiling system; or (2) integrated into theceiling tile.
 45. The barrier according to claim 44 wherein thesuspended ceiling system and the light source form an acousticalbarrier.
 46. The barrier according to claim 44 wherein the light sourcefurther comprises push pin contacts for mounting said light source tothe ceiling tile.
 47. The barrier according to claim 44 wherein theentire surface of the barrier that faces an occupant portion of aninternal space is covered with a light transmitting thermally conductivescrim layer. 48.-53. (canceled)